WorldWideScience

Sample records for charged polymer lattices

  1. Fractional lattice charge transport

    Science.gov (United States)

    Flach, Sergej; Khomeriki, Ramaz

    2017-01-01

    We consider the dynamics of noninteracting quantum particles on a square lattice in the presence of a magnetic flux α and a dc electric field E oriented along the lattice diagonal. In general, the adiabatic dynamics will be characterized by Bloch oscillations in the electrical field direction and dispersive ballistic transport in the perpendicular direction. For rational values of α and a corresponding discrete set of values of E(α) vanishing gaps in the spectrum induce a fractionalization of the charge in the perpendicular direction - while left movers are still performing dispersive ballistic transport, the complementary fraction of right movers is propagating in a dispersionless relativistic manner in the opposite direction. Generalizations and the possible probing of the effect with atomic Bose-Einstein condensates and photonic networks are discussed. Zak phase of respective band associated with gap closing regime has been computed and it is found converging to π/2 value. PMID:28102302

  2. From lattice gases to polymers

    NARCIS (Netherlands)

    Frenkel, D.

    1990-01-01

    The modification of a technique that was developed to study time correlations in lattice-gas cellular automata to facilitate the numerical simulation of chain molecules is described. As an example, the calculation of the excess chemical potential of an ideal polymer in a dense colloidal

  3. Topological Charge of Lattice Abelian Gauge Theory

    CERN Document Server

    Fujiwara, T; Wu, K

    2001-01-01

    Configuration space of abelian gauge theory on a periodic lattice becomes topologically disconnected by excising exceptional gauge field configurations. It is possible to define a U(1) bundle from the nonexceptional link variables by a smooth interpolation of the transition functions. The lattice analogue of Chern character obtained by a cohomological technique based on the noncommutative differential calculus is shown to give a topological charge related to the topological winding number of the U(1) bundle.

  4. Nanotribology of charged polymer brushes

    Science.gov (United States)

    Klein, Jacob

    Polymers at surfaces, whose modern understanding may be traced back to early work by Sam Edwards1, have become a paradigm for modification of surface properties, both as steric stabilizers and as remarkable boundary lubricants2. Charged polymer brushes are of particular interest, with both technological implications and especially biological relevance where most macromolecules are charged. In the context of biolubrication, relevant in areas from dry eye syndrome to osteoarthritis, charged polymer surface phases and their complexes with other macromolecules may play a central role. The hydration lubrication paradigm, where tenaciously-held yet fluid hydration shells surrounding ions or zwitterions serve as highly-efficient friction-reducing elements, has been invoked to understand the excellent lubrication provided both by ionized3 and by zwitterionic4 brushes. In this talk we describe recent advances in our understanding of the nanotribology of such charged brush systems. We consider interactions between charged end-grafted polymers, and how one may disentangle the steric from the electrostatic surface forces5. We examine the limits of lubrication by ionized brushes, both synthetic and of biological origins, and how highly-hydrated zwitterionic chains may provide extremely effective boundary lubrication6. Finally we describe how the lubrication of articular cartilage in the major joints, a tribosystem presenting some of the greatest challenges and opportunities, may be understood in terms of a supramolecular synergy between charged surface-attached polymers and zwitterionic groups7. Work supported by European Research Council (HydrationLube), Israel Science Foundation (ISF), Petroleum Research Fund of the American Chemical Society, ISF-NSF China Joint Program.

  5. Annealed Scaling for a Charged Polymer

    Science.gov (United States)

    Caravenna, F.; den Hollander, F.; Pétrélis, N.; Poisat, J.

    2016-03-01

    This paper studies an undirected polymer chain living on the one-dimensional integer lattice and carrying i.i.d. random charges. Each self-intersection of the polymer chain contributes to the interaction Hamiltonian an energy that is equal to the product of the charges of the two monomers that meet. The joint probability distribution for the polymer chain and the charges is given by the Gibbs distribution associated with the interaction Hamiltonian. The focus is on the annealed free energy per monomer in the limit as the length of the polymer chain tends to infinity. We derive a spectral representation for the free energy and use this to prove that there is a critical curve in the parameter plane of charge bias versus inverse temperature separating a ballistic phase from a subballistic phase. We show that the phase transition is first order. We prove large deviation principles for the laws of the empirical speed and the empirical charge, and derive a spectral representation for the associated rate functions. Interestingly, in both phases both rate functions exhibit flat pieces, which correspond to an inhomogeneous strategy for the polymer to realise a large deviation. The large deviation principles in turn lead to laws of large numbers and central limit theorems. We identify the scaling behaviour of the critical curve for small and for large charge bias. In addition, we identify the scaling behaviour of the free energy for small charge bias and small inverse temperature. Both are linked to an associated Sturm-Liouville eigenvalue problem. A key tool in our analysis is the Ray-Knight formula for the local times of the one-dimensional simple random walk. This formula is exploited to derive a closed form expression for the generating function of the annealed partition function, and for several related quantities. This expression in turn serves as the starting point for the derivation of the spectral representation for the free energy, and for the scaling theorems

  6. Annealed Scaling for a Charged Polymer

    Energy Technology Data Exchange (ETDEWEB)

    Caravenna, F., E-mail: francesco.caravenna@unimib.it [Università degli Studi di Milano-Bicocca, Dipartimento di Matematica e Applicazioni (Italy); Hollander, F. den, E-mail: denholla@math.leidenuniv.nl [Leiden University, Mathematical Institute (Netherlands); Pétrélis, N., E-mail: nicolas.petrelis@univ-nantes.fr [Université de Nantes, Laboratoire de Mathématiques Jean Leray UMR 6629 (France); Poisat, J., E-mail: poisat@ceremade.dauphine.fr [Université Paris-Dauphine, PSL Research University, CEREMADE, UMR 7534 (France)

    2016-03-15

    This paper studies an undirected polymer chain living on the one-dimensional integer lattice and carrying i.i.d. random charges. Each self-intersection of the polymer chain contributes to the interaction Hamiltonian an energy that is equal to the product of the charges of the two monomers that meet. The joint probability distribution for the polymer chain and the charges is given by the Gibbs distribution associated with the interaction Hamiltonian. The focus is on the annealed free energy per monomer in the limit as the length of the polymer chain tends to infinity. We derive a spectral representation for the free energy and use this to prove that there is a critical curve in the parameter plane of charge bias versus inverse temperature separating a ballistic phase from a subballistic phase. We show that the phase transition is first order. We prove large deviation principles for the laws of the empirical speed and the empirical charge, and derive a spectral representation for the associated rate functions. Interestingly, in both phases both rate functions exhibit flat pieces, which correspond to an inhomogeneous strategy for the polymer to realise a large deviation. The large deviation principles in turn lead to laws of large numbers and central limit theorems. We identify the scaling behaviour of the critical curve for small and for large charge bias. In addition, we identify the scaling behaviour of the free energy for small charge bias and small inverse temperature. Both are linked to an associated Sturm-Liouville eigenvalue problem. A key tool in our analysis is the Ray-Knight formula for the local times of the one-dimensional simple random walk. This formula is exploited to derive a closed form expression for the generating function of the annealed partition function, and for several related quantities. This expression in turn serves as the starting point for the derivation of the spectral representation for the free energy, and for the scaling theorems

  7. Quasilocal charges in integrable lattice systems

    Science.gov (United States)

    Ilievski, Enej; Medenjak, Marko; Prosen, Tomaž; Zadnik, Lenart

    2016-06-01

    We review recent progress in understanding the notion of locality in integrable quantum lattice systems. The central concept concerns the so-called quasilocal conserved quantities, which go beyond the standard perception of locality. Two systematic procedures to rigorously construct families of quasilocal conserved operators based on quantum transfer matrices are outlined, specializing on anisotropic Heisenberg XXZ spin-1/2 chain. Quasilocal conserved operators stem from two distinct classes of representations of the auxiliary space algebra, comprised of unitary (compact) representations, which can be naturally linked to the fusion algebra and quasiparticle content of the model, and non-unitary (non-compact) representations giving rise to charges, manifestly orthogonal to the unitary ones. Various condensed matter applications in which quasilocal conservation laws play an essential role are presented, with special emphasis on their implications for anomalous transport properties (finite Drude weight) and relaxation to non-thermal steady states in the quantum quench scenario.

  8. Lattice polymers with hydrogen bondlike interactions

    Science.gov (United States)

    Buzano, C.; Pretti, M.

    2002-12-01

    We study the phase behavior of two lattice polymer models (self-avoiding walks) incorporating attractive short-range interactions between parallel chain sections, attempting to mimick hydrogen bonding between monomers. The investigation is carried out in the framework of the Bethe approximation on a hypercubic lattice. The former model, which includes attraction between parallel sections longer than one chain segment, has been recently studied in full detail in the two-dimensional case, by means of accurate numerical transfer matrix techniques, and displays a first-order transition from a swollen ("coil") state to a collapsed ordered ("solid") state. Our investigation on this model is mainly meant to show that the Bethe approximation is able to recover such a behavior, and to extend the result to three dimensions. The latter model is similar, but takes into account attractive interactions also between one segment long parallel sections, which have no reason to be neglected in principle. We obtain, both in two and three dimensions, two phase transitions: An ordinary theta-collapse from the coil state to an isotropic compact ("globule") state, and a first-order transition from the globule to the solid phase. Such results are compared with those of previously investigated polymer models, and their relevance to describe the formation of protein secondary structure is also briefly discussed.

  9. Backward Charge Transfer in Conjugated Polymers

    Institute of Scientific and Technical Information of China (English)

    CHENG Meng-Xing; LI Guang-Qi; Thomas F. George; SUN Xin

    2005-01-01

    It has been known that the static polarizability of a polymer chain with a biexciton is negative. In order to understand this peculiar fact, this paper studies the dynamical process of the charge transfer in the polymer chain induced by an external electric field E during forming the biexciton. The time dependence of the charge distribution in the chain reveals that the charge transfer is backward: the positive charge shifts in the opposite direction of the external electric field. Such a backward charge transfer (BCT) produces an opposite dipole, which makes the polarization negative. The effect of electron interaction on the BCT is illustrated.

  10. Enhancement of polymer dye lasers by multifunctional photonic crystal lattice

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Xiao, Sanshui; Mortensen, Asger

    2009-01-01

    The light output of dye doped hybrid polymer band-edge lasers is increased more than 100 times by using a rectangular lattice photonic crystal, which provides both feedback and couples more pump light into the laser.......The light output of dye doped hybrid polymer band-edge lasers is increased more than 100 times by using a rectangular lattice photonic crystal, which provides both feedback and couples more pump light into the laser....

  11. Location of the adsorption transition for lattice polymers

    Science.gov (United States)

    Madras, Neal

    2017-02-01

    We consider various lattice models of polymers: lattice trees, lattice animals, and self-avoiding walks. The polymer interacts with a surface (hyperplane), receiving an energy reward of β for each site in the surface. It is known that there is an adsorption transition at a critical value of β. We present a new proof of the result of Hammersley et al (1982 J. Phys. A: Math. Gen. 15 539-71) that the transition occurs at a strictly positive value of β when the surface is impenetrable, i.e. when the polymer is restricted to a half-space. In contrast, for a penetrable surface, it is an open problem to prove that the transition occurs at β =0 . We reduce this problem to proving that the fraction of N-site polymers whose span is less than N/{{log}2}N is not too small.

  12. Charge Injection and Transport in Conjugated Polymers.

    Science.gov (United States)

    Malliaras, George

    2007-03-01

    We will overview the state-of-the-art in our understanding of charge injection and transport in conjugated polymers. We start by discussing the identifying characteristics of this class of materials, especially in relation with their structure and morphology. We follow by reviewing the advantages and limitations of experimental techniques that are used to probe charge transport. We then embark on a discussion of the fundamentals of charge transport in organics. We follow a didactic approach, where we start from transport in crystalline semiconductors and gradually introduce corrections for space charge effects, for the influence of disorder on mobility, for high charge densities, and for electric field-dependent charge densities. We compare with experimental data from polyfluorenes. We then shift our attention to charge injection. We review some of the recent theories and compared their predictions to experimental data, again from polyfluorenes. We close by proposing directions for future work.

  13. Charge-transport model for conducting polymers

    Science.gov (United States)

    Dongmin Kang, Stephen; Jeffrey Snyder, G.

    2016-11-01

    The growing technological importance of conducting polymers makes the fundamental understanding of their charge transport extremely important for materials and process design. Various hopping and mobility edge transport mechanisms have been proposed, but their experimental verification is limited to poor conductors. Now that advanced organic and polymer semiconductors have shown high conductivity approaching that of metals, the transport mechanism should be discernible by modelling the transport like a semiconductor with a transport edge and a transport parameter s. Here we analyse the electrical conductivity and Seebeck coefficient together and determine that most polymers (except possibly PEDOT:tosylate) have s = 3 and thermally activated conductivity, whereas s = 1 and itinerant conductivity is typically found in crystalline semiconductors and metals. The different transport in polymers may result from the percolation of charge carriers from conducting ordered regions through poorly conducting disordered regions, consistent with what has been expected from structural studies.

  14. A lattice Boltzmann method for dilute polymer solutions.

    Science.gov (United States)

    Singh, Shiwani; Subramanian, Ganesh; Ansumali, Santosh

    2011-06-13

    We present a lattice Boltzmann approach for the simulation of non-Newtonian fluids. The method is illustrated for the specific case of dilute polymer solutions. With the appropriate local equilibrium distribution, phase-space dynamics on a lattice, driven by a Bhatnagar-Gross-Krook (BGK) relaxation term, leads to a solution of the Fokker-Planck equation governing the probability density of polymer configurations. Results for the bulk rheological characteristics for steady and start-up shear flow are presented, and compare favourably with those obtained using Brownian dynamics simulations. The new method is less expensive than stochastic simulation techniques, particularly in the range of small to moderate Weissenberg numbers (Wi).

  15. Baryon number and charge fluctuations from lattice QCD

    CERN Document Server

    Schmidt, Christian

    2012-01-01

    We calculate electric and baryonic charge fluctuations on the lattice. Results have been obtained with the highly improved staggered quark action (HISQ) and almost physical quark masses on lattices with spacial extent of $N_\\tau=6,8,12$. Higher order cumulants of the net-charge distributions are increasingly dominated by a universal scaling behavior, which is arising due to a critical point of QCD in the chiral limit. Considering cumulants up to the sixth order, we observe that they generically behave as expected from universal scaling laws, which is quite different from the cumulants calculated within the hadron resonance gas model. Taking ratios of these cumulants, we obtain volume independent results that can be compared to the experimental measurements. Such a comparison will unambiguously relate the QCD transition temperature that has been determined on the lattice with the freeze out temperature of heavy ion collision at LHC and RHIC.

  16. Moving charged particles in lattice Boltzmann-based electrokinetics.

    Science.gov (United States)

    Kuron, Michael; Rempfer, Georg; Schornbaum, Florian; Bauer, Martin; Godenschwager, Christian; Holm, Christian; de Graaf, Joost

    2016-12-07

    The motion of ionic solutes and charged particles under the influence of an electric field and the ensuing hydrodynamic flow of the underlying solvent is ubiquitous in aqueous colloidal suspensions. The physics of such systems is described by a coupled set of differential equations, along with boundary conditions, collectively referred to as the electrokinetic equations. Capuani et al. [J. Chem. Phys. 121, 973 (2004)] introduced a lattice-based method for solving this system of equations, which builds upon the lattice Boltzmann algorithm for the simulation of hydrodynamic flow and exploits computational locality. However, thus far, a description of how to incorporate moving boundary conditions into the Capuani scheme has been lacking. Moving boundary conditions are needed to simulate multiple arbitrarily moving colloids. In this paper, we detail how to introduce such a particle coupling scheme, based on an analogue to the moving boundary method for the pure lattice Boltzmann solver. The key ingredients in our method are mass and charge conservation for the solute species and a partial-volume smoothing of the solute fluxes to minimize discretization artifacts. We demonstrate our algorithm's effectiveness by simulating the electrophoresis of charged spheres in an external field; for a single sphere we compare to the equivalent electro-osmotic (co-moving) problem. Our method's efficiency and ease of implementation should prove beneficial to future simulations of the dynamics in a wide range of complex nanoscopic and colloidal systems that were previously inaccessible to lattice-based continuum algorithms.

  17. Charge-carrier mobilities in disordered semiconducting polymers: effects of carrier density and electric field

    Science.gov (United States)

    Meisel, K. D.; Pasveer, W. F.; Cottaar, J.; Tanase, C.; Coehoorn, R.; Bobbert, P. A.; Blom, P. W. M.; de Leeuw, D. M.; Michels, M. A. J.

    2006-02-01

    We model charge transport in disordered semiconducting polymers by hopping of charge carriers on a square lattice of sites with Gaussian on-site energy disorder, using Fermi-Dirac statistics. From numerically exact solutions of the Master equation, we study the dependence of the charge-carrier mobility on temperature, carrier density, and electric field. Our results are used in calculating current-voltage characteristics of hole-only polymer diodes. It is found that very good fits to experimental current-voltage characteristics can be obtained at different temperatures, with reasonable fitting parameters for the width of the Gaussian density of states and the lattice constant. In agreement with the experiments we find that the density dependence is dominant over the field dependence. Only at high fields and low temperatures the field dependence becomes noticeable. The potential and current distribution show strong inhomogeneities, which may have important consequences for the operation of polymer opto-electronic devices.

  18. A general relationship between disorder, aggregation and charge transport in conjugated polymers

    KAUST Repository

    Noriega, Rodrigo

    2013-08-04

    Conjugated polymer chains have many degrees of conformational freedom and interact weakly with each other, resulting in complex microstructures in the solid state. Understanding charge transport in such systems, which have amorphous and ordered phases exhibiting varying degrees of order, has proved difficult owing to the contribution of electronic processes at various length scales. The growing technological appeal of these semiconductors makes such fundamental knowledge extremely important for materials and process design. We propose a unified model of how charge carriers travel in conjugated polymer films. We show that in high-molecular-weight semiconducting polymers the limiting charge transport step is trapping caused by lattice disorder, and that short-range intermolecular aggregation is sufficient for efficient long-range charge transport. This generalization explains the seemingly contradicting high performance of recently reported, poorly ordered polymers and suggests molecular design strategies to further improve the performance of future generations of organic electronic materials. © 2013 Macmillan Publishers Limited. All rights reserved.

  19. Moving Charged Particles in Lattice Boltzmann-Based Electrokinetics

    CERN Document Server

    Kuron, Michael; Schornbaum, Florian; Bauer, Martin; Godenschwager, Christian; Holm, Christian; de Graaf, Joost

    2016-01-01

    The motion of ionic solutes and charged particles under the influence of an electric field and the ensuing hydrodynamic flow of the underlying solvent is ubiquitous in aqueous colloidal suspensions. The physics of such systems is described by a coupled set of differential equations, along with boundary conditions, collectively referred to as the electrokinetic equations. Capuani et al. [J. Chem. Phys. 121, 973 (2004)] introduced a lattice-based method for solving this system of equations, which builds upon the lattice Boltzmann (LB) algorithm for the simulation of hydrodynamic flow and exploits computational locality. However, thus far, a description of how to incorporate moving boundary conditions, which are needed to simulate moving colloids, into the Capuani scheme has been lacking. In this paper, we detail how to introduce such moving boundaries, based on an analogue to the moving boundary method for the pure LB solver. The key ingredients in our method are mass and charge conservation for the solute spec...

  20. Evidence of Ultrafast Charge Transfer Driven by Coherent Lattice Vibrations.

    Science.gov (United States)

    Rury, Aaron S; Sorenson, Shayne A; Dawlaty, Jahan M

    2017-01-05

    We report evidence that intermolecular vibrations coherently drive charge transfer between the sites of a material on ultrafast time scales. Following a nonresonant stimulated Raman pump pulse that excites the organic material quinhydrone, we observe the initial appearance of oscillations due to intermolecular lattice vibrations and then the delayed appearance of a higher-frequency oscillation that we assign to a totally symmetric intramolecular vibration. We use the coherent dynamics of the transient reflectivity signal to propose that coherence transfer drives excitation of this intramolecular vibration. Furthermore, we conclude that the dynamical frequency shift of the intramolecular vibration reports the formation of a quasi-stable charge-separated state on ultrafast time scales. We calculate model dynamics using the extended Hubbard Hamiltonian to explain coherence transfer due to vibrationally driven charge transfer. These results demonstrate that the coherent excitation of low-frequency vibrations can drive charge transfer in the solid state and control material properties.

  1. Comparison of different lattice definitions of the topological charge

    CERN Document Server

    Cichy, Krzysztof; Garcia-Ramos, Elena; Ottnad, Konstantin; Urbach, Carsten; Wagner, Marc; Wenger, Urs; Zimmermann, Falk

    2014-01-01

    We present a comparison of different definitions of the topological charge on the lattice, using a small-volume ensemble with 2 flavours of dynamical twisted mass fermions. The investigated definitions are: index of the overlap Dirac operator, spectral projectors, spectral flow of the Hermitian Wilson-Dirac operator and field theoretic with different kinds of smoothing of gauge fields (HYP and APE smearings, gradient flow, cooling). We also show some results on the topological susceptibility.

  2. Comparison of different lattice definitions of the topological charge

    Energy Technology Data Exchange (ETDEWEB)

    Cichy, Krzysztof [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Poznan Univ. (Poland). Faculty of Physics; Dromard, Arthur; Wagner, Marc [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Garcia-Ramos, Elena [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Humboldt-Universitaet, Berlin (Germany); Ottnad, Konstantin [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Bonn Univ. (Germany). Helmholtz-Inst. fuer Strahlen- und Kernphysik (Theorie); Bonn Univ. (Germany). Bethe Center for Theoretical Physics; Urbach, Carsten; Zimmermann, Falk [Bonn Univ. (Germany). Helmholtz-Inst. fuer Strahlen- und Kernphysik (Theorie); Bonn Univ. (Germany). Bethe Center for Theoretical Physics; Wenger, Urs [Bern Univ. (Switzerland). Inst. for Theoretical Physics

    2014-11-15

    We present a comparison of different definitions of the topological charge on the lattice, using a small-volume ensemble with 2 flavours of dynamical twisted mass fermions. The investigated definitions are: index of the overlap Dirac operator, spectral projectors, spectral flow of the Hermitian Wilson-Dirac operator and field theoretic with different kinds of smoothing of gauge fields (HYP and APE smearings, gradient flow, cooling). We also show some results on the topological susceptibility.

  3. Magnetic charge lattices, moduli spaces and fusion rules

    Energy Technology Data Exchange (ETDEWEB)

    Kampmeijer, L. [Institute for Theoretical Physics, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands)], E-mail: leo.kampmeijer@uva.nl; Slingerland, J.K. [Dublin Institute for Advanced Studies, School for Theoretical Physics, 10 Burlington Rd, Dublin (Ireland)], E-mail: slingerland@stp.dias.ie; Schroers, B.J. [Department of Mathematics, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS (United Kingdom)], E-mail: bernd@ma.hw.ac.uk; Bais, F.A. [Institute for Theoretical Physics, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands)], E-mail: bais@science.uva.nl

    2009-01-01

    We analyze the labelling and fusion properties of magnetic charge sectors consisting of smooth BPS monopoles in Yang-Mills-Higgs theory with arbitrary gauge group G spontaneously broken to a subgroup H. The magnetic charges are restricted by a generalized Dirac quantization condition and by an inequality due to Murray. Geometrically, the set of allowed charges is a solid cone in the coroot lattice of G, which we call the Murray cone. We argue that magnetic charge sectors correspond to points in this cone divided by the Weyl group of H so that magnetic charge sectors are labelled by dominant integral weights of the dual group H*. We define generators of the Murray cone modulo Weyl group, and interpret the monopoles in the associated magnetic charge sectors as basic; monopoles in sectors with decomposable charges are interpreted as composite configurations. This interpretation is supported by the dimensionality of the moduli spaces associated to the magnetic charges and by classical fusion properties for smooth monopoles in particular cases. Throughout the paper we compare our findings with corresponding results for singular monopoles recently obtained by Kapustin and Witten.

  4. The effect of interface hopping on inelastic scattering of oppositely charged polarons in polymers

    Institute of Scientific and Technical Information of China (English)

    Di Bing; Wang Ya-Dong; Zhang Ya-Lin; An Zhong

    2013-01-01

    The inelastic scattering of oppositely charge polarons in polymer heterojunctions is believed to be of fundamental importance for the light-emitting and transport properties of conjugated polymers.Based on the tight-binding SSH model,and by using a nonadiabatic molecular dynamic method,we investigate the effects of interface hopping on inelastic scattering of oppositely charged polarons in a polymer heterojunction.It is found that the scattering processes of the charge and lattice defect depend sensitively on the hopping integrals at the polymer/polymer interface when the interface potential barrier and applied electric field strength are constant.In particular,at an intermediate electric field,when the interface hopping integral of the polymer/polymer heterojunction material is increased beyond a critical value,two polarons can combine to become a lattice deformation in one of the two polymer chains,with the electron and the hole bound together,i.e.,a self-trapped polaron-exciton.The yield of excitons then increases to a peak value.These results show that interface hopping is of fundamental importance and facilitates the formation of polaron-excitons.

  5. SHAPE OF POLYMER CHAINS ON A TETRAHEDRAL LATTICE

    Institute of Scientific and Technical Information of China (English)

    Jian-hua Huang; Me+ng-bo Luo; Wen-hua Jiang; Shi-jun Han

    2000-01-01

    The shape of unperturbed polymer chains was studied using the Monte Carlo technique on a tetrahedral lattice.The asphericity A, the ratios / and / were calculated for different values of polymer chain length n,conformational energy ε (ε≥ 0) and temperature T. The asphericity A decreases with the increase of chain length and tends to reach its limiting value rapidly with the decrease of γ (γ = ε/kBT). For large n, A is about 0.525 ± 0.005, the ratios/ and / are about 2.7 and 12.0, respectively, and are almost independent of γ, but for short chains, they depend on γ.

  6. Photoinduced Transformation between Charge Carrier and Spin Carrier in Polymers

    Institute of Scientific and Technical Information of China (English)

    MEI Yuan; ZHAO Chang; SUN Xin

    2006-01-01

    By dynamical simulations, we show a transforming process between neutral soliton (spin carrier) and charged soliton (charge carrier) in polymers via photo-excitation, taking a polaron as the transitional bridge. It is photoinduced transformation between spin carrier and charge carrier. In this way, we demonstrate an access for polymers to be applied to spintronics.

  7. Lattice cluster theory for polymer melts with specific interactions

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wen-Sheng, E-mail: wsxu@uchicago.edu [James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Freed, Karl F., E-mail: freed@uchicago.edu [James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Department of Chemistry, The University of Chicago, Chicago, Illinois 60637 (United States)

    2014-07-28

    Despite the long-recognized fact that chemical structure and specific interactions greatly influence the thermodynamic properties of polymer systems, a predictive molecular theory that enables systematically addressing the role of chemical structure and specific interactions has been slow to develop even for polymer melts. While the lattice cluster theory (LCT) provides a powerful vehicle for understanding the influence of various molecular factors, such as monomer structure, on the thermodynamic properties of polymer melts and blends, the application of the LCT has heretofore been limited to the use of the simplest polymer model in which all united atom groups within the monomers of a species interact with a common monomer averaged van der Waals energy. Thus, the description of a compressible polymer melt involves a single van der Waals energy. As a first step towards developing more realistic descriptions to aid in the analysis of experimental data and the design of new materials, the LCT is extended here to treat models of polymer melts in which the backbone and side groups have different interaction strengths, so three energy parameters are present, namely, backbone-backbone, side group-side group, and backbone-side group interaction energies. Because of the great algebraic complexity of this extension, we retain maximal simplicity within this class of models by further specializing this initial study to models of polymer melts comprising chains with poly(n-α-olefin) structures where only the end segments on the side chains may have different, specific van der Waals interaction energies with the other united atom groups. An analytical expression for the LCT Helmholtz free energy is derived for the new model. Illustrative calculations are presented to demonstrate the degree to which the thermodynamic properties of polymer melts can be controlled by specific interactions.

  8. An analytic map for space charge in a nonlinear lattice

    Energy Technology Data Exchange (ETDEWEB)

    Benedetti, C. [Dipartimento di Fisica Universita di Bologna and INFN, Via Irnerio 46, 40126 Bologna (Italy)]. E-mail: benedetti@bo.infn.it; Turchetti, G. [Dipartimento di Fisica Universita di Bologna and INFN, Via Irnerio 46, 40126 Bologna (Italy)

    2005-06-13

    We propose a simple analytical model for an intense beam in a lattice with localized nonlinearities. In the thin lens limit a single nonlinearity leads to a Henon like map. When the space charge is present and the core radius is small with respect to the dynamic aperture, the use of a frozen core distribution like KV is justified. In this case we define an analytic map M by composing the phase advance due to space charge, computed at the first perturbation order, with the kick due to the nonlinear force. The corresponding dynamics is almost indistinguishable from the dynamics of the 'exact' map, which requires an accurate symplectic integration, if the tune depression is weak enough. The same accuracy is preserved for parametric modulations of the perveance or the beam core radius. The extension to any other distribution is straightforward.

  9. Lattice cluster theory for dense, thin polymer films.

    Science.gov (United States)

    Freed, Karl F

    2015-04-07

    While the application of the lattice cluster theory (LCT) to study the miscibility of polymer blends has greatly expanded our understanding of the monomer scale molecular details influencing miscibility, the corresponding theory for inhomogeneous systems has not yet emerged because of considerable technical difficulties and much greater complexity. Here, we present a general formulation enabling the extension of the LCT to describe the thermodynamic properties of dense, thin polymer films using a high dimension, high temperature expansion. Whereas the leading order of the LCT for bulk polymer systems is essentially simple Flory-Huggins theory, the highly non-trivial leading order inhomogeneous LCT (ILCT) for a film with L layers already involves the numerical solution of 3(L - 1) coupled, highly nonlinear equations for the various density profiles in the film. The new theory incorporates the essential "transport" constraints of Helfand and focuses on the strict imposition of excluded volume constraints, appropriate to dense polymer systems, rather than the maintenance of chain connectivity as appropriate for lower densities and as implemented in self-consistent theories of polymer adsorption at interfaces. The ILCT is illustrated by presenting examples of the computed profiles of the density, the parallel and perpendicular bonds, and the chain ends for free standing and supported films as a function of average film density, chain length, temperature, interaction with support, and chain stiffness. The results generally agree with expected general trends.

  10. Neutron Electric Dipole Moment and Tensor Charges from Lattice QCD.

    Science.gov (United States)

    Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram

    2015-11-20

    We present lattice QCD results on the neutron tensor charges including, for the first time, a simultaneous extrapolation in the lattice spacing, volume, and light quark masses to the physical point in the continuum limit. We find that the "disconnected" contribution is smaller than the statistical error in the "connected" contribution. Our estimates in the modified minimal subtraction scheme at 2 GeV, including all systematics, are g_{T}^{d-u}=1.020(76), g_{T}^{d}=0.774(66), g_{T}^{u}=-0.233(28), and g_{T}^{s}=0.008(9). The flavor diagonal charges determine the size of the neutron electric dipole moment (EDM) induced by quark EDMs that are generated in many new scenarios of CP violation beyond the standard model. We use our results to derive model-independent bounds on the EDMs of light quarks and update the EDM phenomenology in split supersymmetry with gaugino mass unification, finding a stringent upper bound of d_{n}<4×10^{-28} e cm for the neutron EDM in this scenario.

  11. Neutron Electric Dipole Moment and Tensor Charges from Lattice QCD

    CERN Document Server

    Bhattacharya, Tanmoy; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram

    2015-01-01

    We present Lattice QCD results on the neutron tensor charges including, for the first time, a simultaneous extrapolation in the lattice spacing, volume, and light quark masses to the physical point in the continuum limit. We find that the "disconnected" contribution is smaller than the statistical error in the "connected" contribution. Our estimates in the $\\overline{\\text{MS}}$ scheme at $2$ GeV, including all systematics, are $g_T^{d-u}=1.020(76)$, $g_T^d = 0.774(66)$, $g_T^u = - 0.233(28)$, and $g_T^s = 0.008(9)$. The flavor diagonal charges determine the size of the neutron electric dipole moment (EDM) induced by quark EDMs that are generated in many new scenarios of CP-violation beyond the Standard Model (BSM). We use our results to derive model-independent bounds on the EDMs of light quarks and update the EDM phenomenology in split Supersymmetry with gaugino mass unification, finding a stringent upper bound of $d_n < 4 \\times 10^{-28} \\, e$ cm for the neutron EDM in this scenario.

  12. Neutron Electric Dipole Moment and Tensor Charges from Lattice QCD

    Science.gov (United States)

    Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram; Pndme Collaboration

    2015-11-01

    We present lattice QCD results on the neutron tensor charges including, for the first time, a simultaneous extrapolation in the lattice spacing, volume, and light quark masses to the physical point in the continuum limit. We find that the "disconnected" contribution is smaller than the statistical error in the "connected" contribution. Our estimates in the modified minimal subtraction scheme at 2 GeV, including all systematics, are gTd -u=1.020 (76 ), gTd=0.774 (66 ), gTu=-0.233 (28 ), and gTs=0.008 (9 ). The flavor diagonal charges determine the size of the neutron electric dipole moment (EDM) induced by quark EDMs that are generated in many new scenarios of C P violation beyond the standard model. We use our results to derive model-independent bounds on the EDMs of light quarks and update the EDM phenomenology in split supersymmetry with gaugino mass unification, finding a stringent upper bound of dnEDM in this scenario.

  13. Molecular mobility with respect to accessible volume in Monte Carlo lattice model for polymers

    Science.gov (United States)

    Diani, J.; Gilormini, P.

    2017-02-01

    A three-dimensional cubic Monte Carlo lattice model is considered to test the impact of volume on the molecular mobility of amorphous polymers. Assuming classic polymer chain dynamics, the concept of locked volume limiting the accessible volume around the polymer chains is introduced. The polymer mobility is assessed by its ability to explore the entire lattice thanks to reptation motions. When recording the polymer mobility with respect to the lattice accessible volume, a sharp mobility transition is observed as witnessed during glass transition. The model ability to reproduce known actual trends in terms of glass transition with respect to material parameters, is also tested.

  14. Charge transfer and transport in polymer-fullerene solar cells

    NARCIS (Netherlands)

    Parisi, J; Dyakonov, [No Value; Pientka, M; Riedel, [No Value; Deibel, C; Brabec, CJ; Sariciftci, NS; Hummelen, JC

    2002-01-01

    The development of polymer-fullerene plastic solar cells has made significant progress in recent years. These devices excel by an efficient charge generation process as a consequence of a photoinduced charge transfer between the photo-excited conjugated polymer donor and acceptor-type fullerene

  15. Calculating charge-carrier mobilities in disordered semiconducting polymers: Mean field and beyond

    Science.gov (United States)

    Cottaar, J.; Bobbert, P. A.

    2006-09-01

    We model charge transport in disordered semiconducting polymers by hopping of charges on a regular cubic lattice of sites. A large on-site Coulomb repulsion prohibits double occupancy of the sites. Disorder is introduced by taking random site energies from a Gaussian distribution. Recently, it was demonstrated that this model leads to a dependence of the charge-carrier mobilities on the density of charge carriers that is in agreement with experimental observations. The model is conveniently solved within a mean-field approximation, in which the correlation between the occupational probabilities of different sites is neglected. This approximation becomes exact in the limit of vanishing charge-carrier densities, but needs to be checked at high densities. We perform this check by dividing the lattice in pairs of neighboring sites and taking into account the correlation between the sites within each pair explicitly. This pair approximation is expected to account for the most important corrections to the mean-field approximation. We study the effects of varying temperature, charge-carrier density, and electric field. We demonstrate that in the parameter regime relevant for semiconducting polymers used in practical devices the corrections to the mobilities calculated from the mean-field approximation will not exceed a few percent, so that this approximation can be safely used.

  16. Like-charge attraction and opposite-charge decomplexation between polymers and DNA molecules

    Science.gov (United States)

    Buyukdagli, Sahin

    2017-02-01

    We scrutinize the effect of polyvalent ions on polymer-DNA interactions. We extend a recently developed test-charge theory [S. Buyukdagli et al., Phys. Rev. E 94, 042502 (2016), 10.1103/PhysRevE.94.042502] to the case of a stiff polymer interacting with a DNA molecule in an electrolyte mixture. The theory accounts for one-loop level electrostatic correlation effects such as the ionic cloud deformation around the strongly charged DNA molecule as well as image-charge forces induced by the low DNA permittivity. Our model can reproduce and explain various characteristics of the experimental phase diagrams for polymer solutions. First, the addition of polyvalent cations to the electrolyte solution results in the attraction of the negatively charged polymer by the DNA molecule. The glue of the like-charge attraction is the enhanced shielding of the polymer charges by the dense counterion layer at the DNA surface. Second, through the shielding of the DNA-induced electrostatic potential, mono- and polyvalent cations of large concentration both suppress the like-charge attraction. Within the same formalism, we also predict a new opposite-charge repulsion effect between the DNA molecule and a positively charged polymer. In the presence of polyvalent anions such as sulfate or phosphate, their repulsion by the DNA charges leads to the charge screening deficiency of the region around the DNA molecule. This translates into a repulsive force that results in the decomplexation of the polymer from DNA. This opposite-charge repulsion phenomenon can be verified by current experiments and the underlying mechanism can be beneficial to gene therapeutic applications where the control over polymer-DNA interactions is the key factor.

  17. Chaotic phenomena of charged particles in crystal lattices.

    Science.gov (United States)

    Desalvo, Agostino; Giannerini, Simone; Rosa, Rodolfo

    2006-06-01

    In this article, we have applied the methods of chaos theory to channeling phenomena of positive charged particles in crystal lattices. In particular, we studied the transition between two ordered types of motion; i.e., motion parallel to a crystal axis (axial channeling) and to a crystal plane (planar channeling), respectively. The transition between these two regimes turns out to occur through an angular range in which the particle motion is highly disordered and the region of phase space spanned by the particle is much larger than the one swept in the two ordered motions. We have evaluated the maximum Lyapunov exponent with the method put forward by Rosenstein et al. [Physica D 65, 117 (1993)] and by Kantz [Phys. Lett. A 185, 77 (1994)]. Moreover, we estimated the correlation dimension by using the Grassberger-Procaccia method. We found that at the transition the system exhibits a very complex behavior showing an exponential divergence of the trajectories corresponding to a positive Lyapunov exponent and a noninteger value of the correlation dimension. These results turn out to be linked to a physical interpretation. The Lyapunov exponents are in agreement with the model by Akhiezer et al. [Phys. Rep. 203, 289 (1991)], based on the equivalence between the ion motion along the crystal plane described as a "string of strings" and the "kicked" rotator. The nonintegral value of the correlation dimension can be explained by the nonconservation of transverse energy at the transition.

  18. Charge-carrier mobilities in disordered semiconducting polymers: effects of carrier density and electric field

    Energy Technology Data Exchange (ETDEWEB)

    Meisel, K.D.; Pasveer, W.F.; Cottaar, J.; Bobbert, P.A.; Michels, M.A.J. [Group Polymer Physics, Eindhoven Polymer Laboratories and Dutch Polymer Institute, Technische Universiteit Eindhoven, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Tanase, C.; Blom, P.W.M. [Materials Science Centre and Dutch Polymer Institute, Nijenborgh 4, 9747 AG Groningen (Netherlands); Coehoorn, R.; Leeuw, D.M. de [Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA Eindhoven (Netherlands)

    2006-02-01

    We model charge transport in disordered semiconducting polymers by hopping of charge carriers on a square lattice of sites with Gaussian on-site energy disorder, using Fermi-Dirac statistics. From numerically exact solutions of the Master equation, we study the dependence of the charge-carrier mobility on temperature, carrier density, and electric field. Our results are used in calculating current-voltage characteristics of hole-only polymer diodes. It is found that very good fits to experimental current-voltage characteristics can be obtained at different temperatures, with reasonable fitting parameters for the width of the Gaussian density of states and the lattice constant. In agreement with the experiments we find that the density dependence is dominant over the field dependence. Only at high fields and low temperatures the field dependence becomes noticeable. The potential and current distribution show strong inhomogeneities, which may have important consequences for the operation of polymer opto-electronic devices. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Statistical mechanics of directed models of polymers in the square lattice

    CERN Document Server

    Rensburg, J V

    2003-01-01

    Directed square lattice models of polymers and vesicles have received considerable attention in the recent mathematical and physical sciences literature. These are idealized geometric directed lattice models introduced to study phase behaviour in polymers, and include Dyck paths, partially directed paths, directed trees and directed vesicles models. Directed models are closely related to models studied in the combinatorics literature (and are often exactly solvable). They are also simplified versions of a number of statistical mechanics models, including the self-avoiding walk, lattice animals and lattice vesicles. The exchange of approaches and ideas between statistical mechanics and combinatorics have considerably advanced the description and understanding of directed lattice models, and this will be explored in this review. The combinatorial nature of directed lattice path models makes a study using generating function approaches most natural. In contrast, the statistical mechanics approach would introduce...

  20. Spectral and structural stability properties of charged particle dynamics in coupled lattices

    CERN Document Server

    Qin, Hong; Davidson, Ronald C; Burby, J W

    2015-01-01

    It has been realized in recent years that coupled focusing lattices in accelerators and storage rings have significant advantages over conventional uncoupled focusing lattices, especially for high-intensity charged particle beams. A theoretical framework and associated tools for analyzing the spectral and structural stability properties of coupled lattices are formulated in this paper, based on the recently developed generalized Courant-Snyder theory for coupled lattices. It is shown that for periodic coupled lattices that are spectrally and structurally stable, the matrix envelope equation must admit matched solutions. Using the technique of normal form and pre-Iwasawa decomposition, a new method is developed to replace the (inefficient) shooting method for finding matched solutions for the matrix envelope equation. Stability properties of a continuously rotating quadrupole lattice are investigated. The Krein collision process for destabilization of the lattice is demonstrated.

  1. Lattice model of linear telechelic polymer melts. I. Inclusion of chain semiflexibility in the lattice cluster theory

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wen-Sheng, E-mail: wsxu@uchicago.edu [James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Freed, Karl F., E-mail: freed@uchicago.edu [James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Department of Chemistry, The University of Chicago, Chicago, Illinois 60637 (United States)

    2015-07-14

    The lattice cluster theory (LCT) for the thermodynamics of polymer systems has recently been reformulated to treat strongly interacting self-assembling polymers composed of fully flexible linear telechelic chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. 136, 064902 (2012)]. Here, we further extend the LCT for linear telechelic polymer melts to include a description of chain semiflexibility, which is treated by introducing a bending energy penalty whenever a pair of consecutive bonds from a single chain lies along orthogonal directions. An analytical expression for the Helmholtz free energy is derived for the model of semiflexible linear telechelic polymer melts. The extension provides a theoretical tool for investigating the influence of chain stiffness on the thermodynamics of self-assembling telechelic polymers, and for further exploring the influence of self-assembly on glass formation in such systems.

  2. Complexation of amyloid fibrils with charged conjugated polymers.

    Science.gov (United States)

    Ghosh, Dhiman; Dutta, Paulami; Chakraborty, Chanchal; Singh, Pradeep K; Anoop, A; Jha, Narendra Nath; Jacob, Reeba S; Mondal, Mrityunjoy; Mankar, Shruti; Das, Subhadeep; Malik, Sudip; Maji, Samir K

    2014-04-01

    It has been suggested that conjugated charged polymers are amyloid imaging agents and promising therapeutic candidates for neurological disorders. However, very less is known about their efficacy in modulating the amyloid aggregation pathway. Here, we studied the modulation of Parkinson's disease associated α-synuclein (AS) amyloid assembly kinetics using conjugated polyfluorene polymers (PF, cationic; PFS, anionic). We also explored the complexation of these charged polymers with the various AS aggregated species including amyloid fibrils and oligomers using multidisciplinary biophysical techniques. Our data suggests that both polymers irrespective of their different charges in the side chains increase the fibrilization kinetics of AS and also remarkably change the morphology of the resultant amyloid fibrils. Both polymers were incorporated/aligned onto the AS amyloid fibrils as evident from electron microscopy (EM) and atomic force microscopy (AFM), and the resultant complexes were structurally distinct from their pristine form of both polymers and AS supported by FTIR study. Additionally, we observed that the mechanism of interactions between the polymers with different species of AS aggregates were markedly different.

  3. Central Charge of the Parallelogram Lattice Strong Coupling Schwinger Model

    CERN Document Server

    Yee, K

    1993-01-01

    We put forth a Fierzed hopping expansion for strong coupling Wilson fermions. As an application, we show that the strong coupling Schwinger model on parallelogram lattices with nonbacktracking Wilson fermions span, as a function of the lattice skewness angle, the $\\Delta = -1$ critical line of $6$-vertex models. This Fierzed formulation also applies to backtracking Wilson fermions, which as we describe apparently correspond to richer systems. However, we have not been able to identify them with exactly solved models.

  4. Maximum-Likelihood Approach to Topological Charge Fluctuations in Lattice Gauge Theory

    CERN Document Server

    Brower, R C; Fleming, G T; Lin, M F; Neil, E T; Osborn, J C; Rebbi, C; Rinaldi, E; Schaich, D; Schroeder, C; Voronov, G; Vranas, P; Weinberg, E; Witzel, O

    2014-01-01

    We present a novel technique for the determination of the topological susceptibility (related to the variance of the distribution of global topological charge) from lattice gauge theory simulations, based on maximum-likelihood analysis of the Markov-chain Monte Carlo time series. This technique is expected to be particularly useful in situations where relatively few tunneling events are observed. Restriction to a lattice subvolume on which topological charge is not quantized is explored, and may lead to further improvement when the global topology is poorly sampled. We test our proposed method on a set of lattice data, and compare it to traditional methods.

  5. Influence of polymer charge on the shear yield stress of silica aggregated with adsorbed cationic polymers.

    Science.gov (United States)

    Zhou, Ying; Yu, Hai; Wanless, Erica J; Jameson, Graeme J; Franks, George V

    2009-08-15

    Flocs were produced by adding three cationic polymers (10% charge density, 3.0x10(5) g/mol molecular weight; 40% charge density, 1.1x10(5) g/mol molecular weight; and 100% charge density, 1.2x10(5) g/mol molecular weight) to 90 nm diameter silica particles. The shear yield stresses of the consolidated sediment beds from settled and centrifuged flocs were determined via the vane technique. The polymer charge density plays an important role in influencing the shear yield stresses of sediment beds. The shear yield stresses of sediment beds from flocs induced by the 10% charged polymer were observed to increase with an increase in polymer dose, initial solid concentration and background electrolyte concentration at all volume fractions. In comparison, polymer dose has a marginal effect on the shear yield stresses of sediment beds from flocs induced by the 40% and 100% charged polymers. The shear yield stresses of sediments from flocs induced by the 40% charged polymer are independent of salt concentration whereas the addition of salt decreases the shear yield stresses of sediments from flocs induced by the 100% charged polymer. When flocculated at the optimum dose for each polymer (12 mg/g silica for the 10% charged polymer at 0.03 M NaCl, 12 mg/g for 40% and 2 mg/g for 100%), shear yield stress increases as polymer charge increases. The effects observed are related to the flocculation mechanism (bridging, patch attraction or charge neutralisation) and the magnitude of the adhesive force. Comparison of shear and compressive yield stresses show that the network is only slightly weaker in shear than in compression. This is different than many other systems (mainly salt and pH coagulation) which have shear yield stress much less than compressive yield stress. The existing models relating the power law exponent of the volume fraction dependence of the shear yield stress to the network fractal structure are not satisfactory to predict all the experimental behaviour.

  6. Charge transport in conducting polymers: insights from impedance spectroscopy.

    Science.gov (United States)

    Rubinson, Judith F; Kayinamura, Yohani P

    2009-12-01

    This tutorial review gives a brief introduction to impedance spectroscopy and discusses how it has been used to provide insight into charge transport through conducting polymers, particularly when the polymers are used as electrodes for solution studies or the design of electrodes for biomedical applications. As such it provides both an introduction to the topic and references to both classic and contemporary work for the more advanced reader.

  7. Effect of Charge Patterning on the Phase Behavior of Polymer Coacervates for Charge Driven Self Assembly

    Science.gov (United States)

    Radhakrishna, Mithun; Sing, Charles E.

    Oppositely charged polymers can undergo associative liquid-liquid phase separation when mixed under suitable conditions of ionic strength, temperature and pH to form what are known as `polymeric complex coacervates'. Polymer coacervates find use in diverse array of applications like microencapsulation, drug delivery, membrane filtration and underwater adhesives. The similarity between complex coacervate environments and those in biological systems has also found relevance in areas of bio-mimicry. Our previous works have demonstrated how local charge correlations and molecular connectivity can drastically affect the phase behavior of coacervates. The precise location of charges along the chain therefore dramatically influences the local charge correlations, which consequently influences the phase behavior of coacervates. We investigate the effect of charge patterning along the polymer chain on the phase behavior of coacervates in the framework of the Restricted Primitive Model using Gibbs Ensemble Monte Carlo simulations. Our results show that charge patterning dramatically changes the phase behavior of polymer coacervates, which contrasts with the predictions of the classical Voorn-Overbeek theory. This provides the basis for designing new materials through charge driven self assembly by controlling the positioning of the charged monomers along the chain.

  8. Simulation of bipolar charge transport in nanocomposite polymer films

    Science.gov (United States)

    Lean, Meng H.; Chu, Wei-Ping L.

    2015-03-01

    This paper describes 3D particle-in-cell simulation of bipolar charge injection and transport through nanocomposite film comprised of ferroelectric ceramic nanofillers in an amorphous polymer matrix. The classical electrical double layer (EDL) model for a monopolar core is extended (eEDL) to represent the nanofiller by replacing it with a dipolar core. Charge injection at the electrodes assumes metal-polymer Schottky emission at low to moderate fields and Fowler-Nordheim tunneling at high fields. Injected particles migrate via field-dependent Poole-Frenkel mobility and recombine with Monte Carlo selection. The simulation algorithm uses a boundary integral equation method for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit assuring robust and rapid convergence. The model is capable of simulating a wide dynamic range spanning leakage current to pre-breakdown. Simulation results for BaTiO3 nanofiller in amorphous polymer matrix indicate that charge transport behavior depend on nanoparticle polarization with anti-parallel orientation showing the highest leakage conduction and therefore lowest level of charge trapping in the interaction zone. Charge recombination is also highest, at the cost of reduced leakage conduction charge. The eEDL model predicts the meandering pathways of charge particle trajectories.

  9. Cell separation in microcanal coated with electrically charged phospholipid polymers.

    Science.gov (United States)

    Ito, Tomomi; Iwasaki, Yasuhiko; Narita, Tadashi; Akiyoshi, Kazunari; Ishihara, Kazuhiko

    2005-03-25

    To separate the cell population in whole blood using microcanal, the surface was covered with a polyion complex (PIC) composed of electrically charged phospholipid polymers. The phospholipids polymers were prepared by the polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and n-butyl methacrylate with 3-(methacryloyloxypropyl)-trimethyl ammonium iodide as the cationic unit or potassium 3-methacryloyloxypropyl sulfonate as the anionic unit. The PIC was formed at the solid-liquid interface, that is, first, the cationic polymer was coated on the substrate and an aqueous solution containing the anionic polymer with different concentrations was applied to the polymer-coated substrate. The formation of the PIC was followed using a quartz crystal microbalance (QCM), and the PIC surfaces were analyzed by both zeta-potential measurement and X-ray photoelectron spectroscopic measurement. The surface electrical potential on the PIC was controllable from +40 to -40 mV by increasing the amount of the adsorbed anionic polymer. The PIC surface was prepared in microcanal. The surface electrical potential was sequentially changed. When the whole blood was introduced into the microcanal, the cells adhered on the positively charged surface, but could not adhere to the negatively charged surface. Even when the cells adhere to the surface, the morphology of cells was maintained. This is due to MPC units at the surface, which show a good biocompatibility. These results indicated that the change in the surface electrical potential will be a useful method to separate the cells from whole blood.

  10. The effect of polymer charge density and charge distribution on the formation of multilayers

    CERN Document Server

    Voigt, U; Tauer, K; Hahn, M; Jäger, W; Klitzing, K V

    2003-01-01

    Polyelectrolyte multilayers which are built up by alternating adsorption of polyanions and polycations from aqueous solutions at a solid interface are investigated by reflectometry and ellipsometry. Below a degree of charge of about 70% the adsorption stops after a certain number of dipping cycles and no multilayer formation occurs. This indicates an electrostatically driven adsorption process. Below a charge density of 70% an adsorption can take place if the charged segments are combined as a block of the polymer.

  11. Molecular Dynamics Simulations of Nanoparticles Coated with Charged Polymers

    Science.gov (United States)

    Wen, Chengyuan; Cheng, Shengfeng

    Polymer coating is frequently used to stabilize colloidal and nano-sized particles. We employ molecular dynamics simulations to study nanoparticles coated with polymer chains that contain ionizable groups. In a polar solvent, the chains become charged with counterions dissociated. In the computational model, we treat the solvent as a uniform dielectric background and use the bead-spring model for the polymer chains. Counterions are explicitly included as mobile beads. The nanoparticle is modeled as a layer of sites uniformly distributed on a spherical surface with a certain fraction of sites serving as the tether points of the grafted polymer brush. We vary the grafting density and calculate the distribution of polymer beads and counterions around the nanoparticle. Our results indicate that charged chains adopt extended conformations because of their mutual repulsions. We further study the interactions between two polymer-coated nanoparticles and obtain the potential of mean force. We also find an interesting transition of a confined single layer of such polymer-coated nanoparticles into two layers when the confinement is removed. Results show that the brush-brush contact has a nonuniform distribution and the nanoparticles tend to form dipole-like structures.

  12. Fractal dimension of the topological charge density distribution in SU(2) lattice gluodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Buividovich, P.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation); Kalaydzhyan, T. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation); Polikarpov, M.I. [Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation)

    2011-11-15

    We study the effect of cooling on the spatial distribution of the topological charge density in quenched SU(2) lattice gauge theory with overlap fermions. We show that as the gauge field configurations are cooled, the Hausdorff dimension of regions where the topological charge is localized gradually changes from d=2/3 towards the total space dimension. Hence the cooling procedure destroys some of the essential properties of the topological charge distribution. (orig.)

  13. Magnetic charge lattices, moduli spaces and fusion rules

    NARCIS (Netherlands)

    Kampmeijer, L.; Slingerland, J.K.; Schroers, B.J.; Bais, F.A.

    2009-01-01

    We analyze the labelling and fusion properties of magnetic charge sectors consisting of smooth BPS monopoles in Yang-Mills-Higgs theory with arbitrary gauge group G spontaneously broken to a subgroup H. The magnetic charges are restricted by a generalized Dirac quantization condition and by an inequ

  14. A Simple Holographic Model of a Charged Lattice

    CERN Document Server

    Aprile, Francesco

    2014-01-01

    We use holography to compute the conductivity in an inhomogeneous charged scalar background. We work in the probe limit of the four-dimensional Einstein-Maxwell theory coupled to a charged scalar. The background has zero charge density and is constructed by turning on a scalar source deformation with a striped profile. We solve for fluctuations by making use of a Fourier series expansion. This approach turns out to be useful for understanding which couplings become important in our inhomogeneous background. At zero temperature, the conductivity is computed analytically in a small amplitude expansion. At finite temperature, it is computed numerically by truncating the Fourier series to a relevant set of modes. In the real part of the conductivity along the direction of the stripe, we find a Drude-like peak and a delta function with a negative weight. These features are understood from the point of view of spectral weight transfer.

  15. Lattice Boltzmann Simulation of Sedimentation of a Single Charged Elastic Dumbbell in a Newtonian Fluid

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chao-Ying; TAN Hui-Li; LIU Mu-Ren; KONG Ling-Jiang; SHI Juan

    2005-01-01

    @@ Based on the lattice Boltzmann method, the sedimentations of elastic dumbbells with different charges in a Newtonian fluid under the same and different initial conditions are simulated.Due to the polarizing effects, there are Coulomb forces exerted on the charged elastic dumbbells during their sedimentations, which change their original motions significantly.All of the numerical results show that, if the charged elastic dumbbells are released at offset-centreline positions with zero velocity and settle under gravity, they fall down vertically off the centreline and their orientations tend to be the horizontal finally, and the distances apart from the centreline increase with the increasing charges of the elastic dumbbells.

  16. Comparison of lattice-Boltzmann and brownian-dynamics simulations of polymer migration in confined flows.

    Science.gov (United States)

    Kekre, Rahul; Butler, Jason E; Ladd, Anthony J C

    2010-07-01

    This paper compares results from lattice-Boltzmann and brownian-dynamics simulations of polymer migration in confined flows bounded by planar walls. We have considered both a uniform shear rate and a constant pressure gradient. Lattice-Boltzmann simulations of the center-of-mass distribution agree quantitatively with brownian-dynamics results, contradicting previously published results. The mean end-to-end distance of the extended polymer is more sensitive to grid resolution Δx and time-step Δt. Nevertheless, for sufficiently small Δx and Δt, convergent results for the polymer stretch are obtained which agree with brownian dynamics within statistical uncertainties. The brownian-dynamics simulations incorporate a mobility matrix for a confined polymer that is both symmetric and positive definite for all physically accessible configurations.

  17. Polymers on disordered hierarchical lattices: A nonlinear combination of random variables

    Energy Technology Data Exchange (ETDEWEB)

    Cook, J. (Commissariat a l' Energie Atomique, Gif-sur-Yvette (France) Univ. of Edinburgh (England)); Derrida, B. (Commissariat a l' Energie Atomique, Gif-sur-Yvette (France))

    1989-10-01

    The problem of directed polymers on disordered hierarchical and hypercubic lattices is considered. For the hierarchical lattices the problem can be reduced to the study of the stable laws for combining random variables in a nonlinear way. The authors present the results of numerical simulations of two hierarchical lattices, finding evidence of a phase transition in one case. For a limiting case they extend the perturbation theory developed by Derrida and Griffiths to nonzero temperature and to higher order and use this approach to calculate thermal and geometrical properties (overlaps) of the model. In this limit they obtain an interpolation formula, allowing one to obtain the noninteger moments of the partition function from the integer moments. They obtain bounds for the transition temperature for hierarchical and hypercubic lattices, and some similarities between the problem on the two different types of lattice are discussed.

  18. Material simulation of charge carrier transport properties of polymer dielectrics

    Science.gov (United States)

    Unge, Mikael; Christen, Thomas; Törnkvist, Christer; ABB Corporate Research Team

    To understand electron and hole transport in solid material requires to know its electronic properties, i.e. the density of states (DOS) and whether the states are spatially localized or delocalized. The states closest to the band edges may be localized, states further away can be delocalized. This transition from localized to delocalized states determines the mobility edge, above the mobility edge the mobility is expected to be high. A real polymer is never perfect; it contains a number of oxidative states, bonding defects and molecular impurities. These imperfections yield electronic states that can appear in the band gap of the polymer, traps. Traps can be shallow, i.e. close to the band edges, from these states the charge carrier easily can jump to a state in the band edge or another shallow state. Other traps can be deep, in these states it is likely that the charge carrier remains and become immobile. All these properties related to the electronic structure of the polymer, including its defects, affects the conductivity of the polymer. Linear scaling Density Functional Theory has been applied to calculate electronic structure of amorphous polyethylene. In particular DOS, trap levels and mobility edges are studied.

  19. Interaction in equilibrium plasmas of charged macroparticles located in nodes of cubic lattices

    Science.gov (United States)

    Filippov, A. V.

    2016-11-01

    Interaction of two charged pointlike macroparticles located at nodes of simple cubic (sc), body-centered cubic (bcc) and face-centered cubic (fcc) lattices in an equilibrium plasma is studied within the linearized Poisson-Boltzmann model. It is shown that the boundary shape has a strong influence on the electrostatic interaction between two macroparticles, which switches from repulsion at small interparticle distances to attraction as it approaches the halflength of a computational cell. It is found that in a case of dust particles arranged in the nodes of the sc, bcc and fcc lattices, the electrostatic force acting on them is equal to zero and the nature of the interaction changes from repulsion to attraction; hence, the infinite sc, bcc and fcc lattices of charged dust particles are thermodynamically stable at rather low temperatures.

  20. A lattice Monte Carlo study of long chain conformations at solid-polymer melt interfaces

    NARCIS (Netherlands)

    Bitsanis, Ioannis A.; Brinke, Gerrit ten

    1993-01-01

    In this paper we present a comprehensive lattice Monte Carlo study of long chain conformations at solid-polymer melt interfaces. Segmental scale interfacial features, like the bond orientational distribution were found to be independent of surface-segment energetics, and statistically identical with

  1. Charge carrier dissociation and recombination in polymer solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Deibel, Carsten [Experimental Physics VI, Julius-Maximilians-University of Wuerzburg, 97074 Wuerzburg (Germany)

    2009-12-15

    In polymer:fullerene solar cells, the origin of the losses in the field-dependent photocurrent is still controversially debated. We contribute to the ongoing discussion by performing photo-induced charge extraction measurements on poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C{sub 61} butyric acid methyl ester solar cells in order to investigate the processes ruling charge carrier decay. Calculating the drift length of photogenerated charges, we find that polaron recombination is not limiting the photocurrent for annealed devices. Additionally, we applied Monte Carlo simulations on blends of conjugated polymer chain donors with acceptor molecules in order to gain insight into the polaron pair dissociation. The dissociation yield turns out to be rather high, with only a weak field dependence. With this complementary view on dissociation and recombination, we stress the importance of accounting for polaron pair dissociation, polaron recombination as well as charge extraction when considering the loss mechanisms in organic solar cells. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  2. Sedimentation of a Single Charged Elliptic Cylinder in a Newtonian Fluid by Lattice Boltzmann Method

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chao-Ying; SHI Juan; TAN Hui-Li; LIU Mu-Ren; KONG Ling-Jiang

    2004-01-01

    @@ We simulate the sedimentation of single charged and single uncharged elliptic cylinders in a Newtonian fluid by using the lattice Boltzmann method. Due to the polarizing effects and non-axial symmetry shape, there are the Coulomb force and corresponding torque exerted on the charged elliptic cylinder during the sedimentation, which significantly change the horizontal translation and rotation of the cylinder. When the dielectric constant of the liquid is smaller than that of the wall, the direction of the Coulomb force is opposite to that of the hydrodynamic force. Therefore there appears to be a critical linear charge density qc at which the elliptic cylinder will fall vertically off the centreline.

  3. Lattice density functional for colloid-polymer mixtures: Comparison of two fundamental measure theories

    Science.gov (United States)

    Cuesta, José A.; Lafuente, Luis; Schmidt, Matthias

    2005-09-01

    We consider a binary mixture of colloid and polymer particles with positions on a simple cubic lattice. Colloids exclude both colloids and polymers from nearest neighbor sites. Polymers are treated as effective particles that are mutually noninteracting, but exclude colloids from neighboring sites; this is a discrete version of the (continuum) Asakura-Oosawa-Vrij model. Two alternative density functionals are proposed and compared in detail. The first is based on multioccupancy in the zero-dimensional limit of the bare model, analogous to the corresponding continuum theory that reproduces the bulk fluid free energy of free volume theory. The second is based on mapping the polymers onto a multicomponent mixture of polymer clusters that are shown to behave as hard cores; the corresponding property of the extended model in strong confinement permits direct treatment with lattice fundamental measure theory. Both theories predict the same topology for the phase diagram with a continuous fluid-fcc freezing transition at low polymer fugacity and, upon crossing a tricritical point, a first-order freezing transition for high polymer fugacities with rapidly broadening density jump.

  4. The Optical Signature of Charges in Conjugated Polymers

    Science.gov (United States)

    2016-01-01

    Electrical charge flowing through organic semiconductors drives many of today’s mobile phone displays and television screens, suggesting an internally consistent model of charge-carrier properties in these materials to have manifested. In conjugated polymers, charges give rise to additional absorption of light at wavelengths longer than those absorbed by the electrically neutral species. These characteristic absorption bands are universally being related to the emergence of localized energy levels shifted into the forbidden gap of organic semiconductors due to local relaxation of the molecular geometry. However, the traditional view on these energy levels and their occupation is incompatible with expected changes in electron removal and addition energies upon charging molecules. Here, I demonstrate that local Coulomb repulsion, as captured by nonempirically optimized electronic-structure calculations, restores compatibility and suggests a different origin of the charge-induced optical transitions. These results challenge a widely accepted and long-established picture, but an improved understanding of charge carriers in molecular materials promises a more targeted development of organic and hybrid organic/inorganic (opto-)electronic devices. PMID:27280165

  5. Charge and lattice stripes studies by X-ray absorption spectroscopy

    CERN Document Server

    Oyanagi, H; Bianconi, A

    2002-01-01

    Lattice effects on superconductivity in high Tc oxide superconductors were investigated by X-ray absorption spectroscopy (XAS) giving a snapshot of local lattice distortions with a time scale of 10 sup - sup 1 sup 5 sec. Local structures of Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 , La sub 1 sub . sub 8 sub 5 Sr sub 0 sub . sub 1 sub 5 CuO sub 4 , YBa sub 2 Cu sub 3 O sub y and La sub 1 sub . sub 4 sub 8 Sr sub 0 sub . sub 1 sub 2 Nd sub 0 sub . sub 4 CuO sub 4 were investigated by polarized XAS over a wide temperature range. We found that the local lattice fluctuation in these materials increases at low temperature, segregates into distorted and undistorted domains, and finally forms a charge and lattice stripe. Local lattice distortions involve the elongated in-plane Cu-O bonds which introduce charge fluctuation or instability leading to ordering into localized and itinerant domains. Also at characteristic temperatures such as Tc and T, pronounced phonon anomalies were observed in the in-plane Cu-O stretching v...

  6. Charge transfer excitons in C60-dimers and polymers

    CERN Document Server

    Harigaya, K

    1996-01-01

    Charge-transfer (CT) exciton effects are investigated for the optical absorption spectra of crosslinked C60 systems by using the intermediate exciton theory. We consider the C60-dimers, and the two (and three) molecule systems of the C60-polymers. We use a tight-binding model with long-range Coulomb interactions among electrons, and the model is treated by the Hartree-Fock approximation followed by the single-excitation configuration interaction method. We discuss the variations in the optical spectra by changing the conjugation parameter between molecules. We find that the total CT-component increases in smaller conjugations, and saturates at the intermediate conjugations. It decreases in the large conjugations. We also find that the CT-components of the doped systems are smaller than those of the neutral systems, indicating that the electron-hole distance becomes shorter in the doped C60-polymers.

  7. On the effect of excited states in lattice calculations of the nucleon axial charge

    CERN Document Server

    Hansen, Maxwell T

    2016-01-01

    Excited-state contamination is one of the dominant uncertainties in lattice calculations of the nucleon axial-charge, $g_A$. Recently published results in leading-order chiral perturbation theory (ChPT) predict the excited-state contamination to be independent of the nucleon interpolator and positive. However, empirical results from numerical lattice calculations show negative contamination (downward curvature), indicating that present-day calculations are not in the regime where the leading-order ChPT predictions apply. In this paper we show that, under plausible assumptions, one can reproduce the behavior of lattice correlators by taking into account final-state $N \\pi$ interactions, in particular the effect of the Roper resonance, and by postulating a sign change in the infinite-volume $N \\to N \\pi$ axial-vector transition amplitude.

  8. Electrolyte transport in neutral polymer gels embedded with charged inclusions

    Science.gov (United States)

    Hill, Reghan

    2005-11-01

    Ion permeable membranes are the basis of a variety of molecular separation technologies, including ion exchange, gel electrophoresis and dialysis. This work presents a theoretical model of electrolyte transport in membranes comprised of a continuous polymer gel embedded with charged spherical inclusions, e.g., biological cells and synthetic colloids. The microstructure mimics immobilized cell cultures, where electric fields have been used to promote nutrient transport. Because several important characteristics can, in principle, be carefully controlled, the theory provides a quantitative framework to help tailor the bulk properties for enhanced molecular transport, microfluidic pumping, and physicochemical sensing applications. This talk focuses on the electroosmotic flow driven by weak electric fields and electrolyte concentration gradients. Also of importance is the influence of charge on the effective ion diffusion coefficients, bulk electrical conductivity, and membrane diffusion potential.

  9. Charged Polymers Transport under Applied Electric Fields in Periodic Channels

    Directory of Open Access Journals (Sweden)

    Sorin Nedelcu

    2013-07-01

    Full Text Available By molecular dynamics simulations, we investigated the transport of charged polymers in applied electric fields in confining environments, which were straight cylinders of uniform or non-uniform diameter. In the simulations, the solvent was modeled explicitly and, also, the counterions and coions of added salt. The electrophoretic velocities of charged chains in relation to electrolyte friction, hydrodynamic effects due to the solvent, and surface friction were calculated. We found that the velocities were higher if counterions were moved away from the polymeric domain, which led to a decrease in hydrodynamic friction. The topology of the surface played a key role in retarding the motion of the polyelectrolyte and, even more so, in the presence of transverse electric fields. The present study showed that a possible way of improving separation resolution is by controlling the motion of counterions or electrolyte friction effects.

  10. Flow-induced charge modulation in superfluid atomic fermions loaded into an optical kagome lattice.

    Science.gov (United States)

    Yamamoto, Daisuke; Sato, Chika; Nikuni, Tetsuro; Tsuchiya, Shunji

    2013-04-05

    We study the superfluid state of atomic fermions in a tunable optical kagome lattice motivated by recent experiments. We show that the imposed superflow induces spatial modulations in the density and order parameter of the pair condensate and leads to a charge modulated superfluid state analogous to a supersolid state. The spatial modulations in the superfluid emerge due to the geometric effect of the kagome lattice that introduces anisotropy in hopping amplitudes of fermion pairs in the presence of superflow. We also study superflow instabilities and find that the critical current limited by the dynamical instability is quite enhanced due to the large density of states associated with the flatband. The charge modulated superfluid state can sustain high temperatures close to the transition temperature that is also enhanced due to the flatband and is therefore realizable in experiments.

  11. Frequency map analysis of resonances in a nonlinear lattice with space charge

    Energy Technology Data Exchange (ETDEWEB)

    Turchetti, G. E-mail: turchetti@bo.infn.it; Bazzani, A.; Bergamini, F.; Rambaldi, S.; Hofmann, I.; Bongini, L.; Franchetti, G

    2001-05-21

    In storage rings for heavy ion fusion beam losses must be minimized. During bunch compression high space charge is reached and the reciprocal effects between the collective modes of the beam and the single particle lattice nonlinearities must be considered to understand the problem of resonance crossing and halo formation. We show that the frequency map analysis of particle in core models gives an adequate description of the resonance network and of the chaotic regions where the halo particles can diffuse.

  12. Axial, scalar, and tensor charges of the nucleon from 2 +1 +1 -flavor Lattice QCD

    Science.gov (United States)

    Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Cohen, Saul D.; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram; Precision Neutron Decay Matrix Elements Pndme Collaboration

    2016-09-01

    We present results for the isovector axial, scalar, and tensor charges gAu -d , gSu -d, and gTu -d of the nucleon needed to probe the Standard Model and novel physics. The axial charge is a fundamental parameter describing the weak interactions of nucleons. The scalar and tensor charges probe novel interactions at the TeV scale in neutron and nuclear β -decays, and the flavor-diagonal tensor charges gTu, gTd, and gTs are needed to quantify the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice-QCD calculations were done using nine ensembles of gauge configurations generated by the MILC Collaboration using the highly improved staggered quarks action with 2 +1 +1 dynamical flavors. These ensembles span three lattice spacings a ≈0.06 ,0.09 , and 0.12 fm and light-quark masses corresponding to the pion masses Mπ≈135 ,225 , and 315 MeV. High-statistics estimates on five ensembles using the all-mode-averaging method allow us to quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, lattice volume, and light-quark masses for the connected contributions. Our final estimates, in the MS ¯ scheme at 2 GeV, of the isovector charges are gAu -d=1.195 (33 )(20 ) , gSu -d=0.97 (12 )(6 ), and gTu -d=0.987 (51 )(20 ) . The first error includes statistical and all systematic uncertainties except that due to the extrapolation Ansatz, which is given by the second error estimate. Combining our estimate for gSu -d with the difference of light quarks masses (md-mu)QCD=2.67 (35 ) MeV given by the Flavor Lattice Average Group, we obtain (MN-MP)QCD=2.59 (49 ) MeV . Estimates of the connected part of the flavor-diagonal tensor charges of the proton are gTu=0.792 (42 ) and gTd=-0.194 (14 ). Combining our new estimates with precision low-energy experiments, we present updated constraints on novel scalar and tensor interactions, ɛS ,T, at the TeV scale.

  13. Coarsening and aging of lattice polymers: Influence of bond fluctuations

    Science.gov (United States)

    Christiansen, Henrik; Majumder, Suman; Janke, Wolfhard

    2017-09-01

    We present results for the nonequilibrium dynamics of collapse for a model flexible homopolymer on simple cubic lattices with fixed and fluctuating bonds between the monomers. Results from our Monte Carlo simulations show that, phenomenologically, the sequence of events observed during the collapse are independent of the bond criterion. While the growth of the clusters (of monomers) at different temperatures exhibits a non-universal power-law behavior when the bonds are fixed, the introduction of fluctuations in the bonds by considering the existence of diagonal bonds produces a temperature independent growth, which can be described by a universal nonequilibrium finite-size scaling function with a non-universal metric factor. We also examine the related aging phenomenon, probed by a suitable two-time density-density autocorrelation function showing a simple power-law scaling with respect to the growing cluster size. Unlike the cluster-growth exponent αc, the nonequilibrium autocorrelation exponent λC governing the aging during the collapse, however, is independent of the bond type and strictly follows the bounds proposed by Majumder and Janke [Phys. Rev. E 93, 032506 (2016)] at all temperatures.

  14. Axial, Scalar and Tensor Charges of the Nucleon from 2+1+1-flavor Lattice QCD

    CERN Document Server

    Bhattacharya, Tanmoy; Cohen, Saul; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram

    2016-01-01

    We present results for the isovector axial, scalar and tensor charges $g^{u-d}_A$, $g^{u-d}_S$ and $g^{u-d}_T$ of the nucleon needed to probe the Standard Model and novel physics. The axial charge is a fundamental parameter describing the weak interactions of nucleons. The scalar and tensor charges probe novel interactions at the TeV scale in neutron and nuclear $\\beta$-decays, and the flavor-diagonal tensor charges $g^{u}_T$, $g^{d}_T$ and $g^{s}_T$ are needed to quantify the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice-QCD calculations were done using nine ensembles of gauge configurations generated by the MILC Collaboration using the HISQ action with 2+1+1 dynamical flavors. These ensembles span three lattice spacings $a \\approx 0.06, 0.09$ and $0.12$ fm and light-quark masses corresponding to the pion masses $M_\\pi \\approx$ 135, 225 and 315 MeV. High-statistics estimates on five ensembles using the all-mode-averaging method allow us to quantify all systematic unce...

  15. Analytical and numerical studies of photo-injected charge transport in molecularly-doped polymers

    Science.gov (United States)

    Roy Chowdhury, Amrita

    The mobility of photo-injected charge carriers in molecularly-doped polymers (MDPs) exhibits a commonly observed, and nearly universal Poole-Frenkel field dependence, mu exp√(beta0E), that has been shown to arise from the correlated Gaussian energy distribution of transport sites encountered by charges undergoing hopping transport through the material. Analytical and numerical studies of photo-injected charge transport in these materials are presented here with an attempt to understand how specific features of the various models developed to describe these systems depend on the microscopic parameters that define them. Specifically, previously published time-of-flight mobility data for the molecularly doped polymer 30% DEH:PC (polycarbonate doped with 30 wt.% aromatic hydrazone DEH) is compared with direct analytical and numerical predictions of five disorder-based models, the Gaussian disorder model (GDM) of Bassler, and four correlated disorder models introduced by Novikov, et al., and by Parris, et al. In these numerical studies, disorder parameters describing each model were varied from reasonable starting conditions, in order to give the best overall fit. The uncorrelated GDM describes the Poole-Frenkel field dependence of the mobility only at very high fields, but fails for fields lower than about 64 V/mum. The correlated disorder models with small amounts of geometrical disorder do a good over-all job of reproducing a robust Poole-Frenkel field dependence, with correlated disorder theories that employ polaron transition rates showing qualitatively better agreement with experiment than those that employ Miller-Abrahams rates. In a separate study, the heuristic treatment of spatial or geometric disorder incorporated in existing theories is critiqued, and a randomly-diluted lattice gas model is developed to describe the spatial disorder of the transport sites in a more realistic way.

  16. Hollow-core polymer fibres with a kagome lattice: potential for transmission in the infrared

    Science.gov (United States)

    Argyros, Alexander; Pla, Jarryd

    2007-06-01

    Hollow-core microstructured polymer optical fibres with a kagome lattice cladding are reported. These fibres do not have photonic bandgaps, instead, leakage from the core is suppressed by a low density of states in the cladding, a low overlap of the core mode and the cladding modes and a reduced susceptibility to perturbations. The latter two are the result of a low overlap between the core mode and the solid parts of the microstructure, which also reduces the absorption by the polymer. Losses two orders of magnitude below the material loss were observed and the potential of hollow-core polymer fibres to guide light in the infrared, where the material absorption is high, will be discussed.

  17. Iso-vector and Iso-scalar Tensor Charges of the Nucleon from Lattice QCD

    CERN Document Server

    Bhattacharya, Tanmoy; Cohen, Saul; Gupta, Rajan; Joseph, Anosh; Lin, Huey-Wen; Yoon, Boram

    2015-01-01

    We present results for the iso-vector and flavor diagonal tensor charges $g^{u-d}_T$, $g^{u}_T$, $g^{d}_T$, and $g^{s}_T$ needed to probe novel tensor interactions at the TeV scale in neutron and nuclear $\\beta$-decays and the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice QCD calculations were done using nine ensembles of gauge configurations generated by the MILC collaboration using the HISQ action with 2+1+1 dynamical flavors. These ensembles span three lattice spacings $a \\approx 0.06, 0.09$ and $0.12 $ fm and three quark masses corresponding to the pion masses $M_\\pi \\approx 130, 220$ and $310 $ MeV. Using estimates from these ensembles, we quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, volume and light quark masses for the connected contributions. The final estimates of the connected nucleon (proton) tensor charge for the iso-vector combination is $g_T^{u-d} = 1.020(76) $ in the $\\overline{\\text{MS}}$ scheme ...

  18. Lattice model of linear telechelic polymer melts. II. Influence of chain stiffness on basic thermodynamic properties

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wen-Sheng, E-mail: wsxu@uchicago.edu [James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Freed, Karl F., E-mail: freed@uchicago.edu [James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Department of Chemistry, The University of Chicago, Chicago, Illinois 60637 (United States)

    2015-07-14

    The lattice cluster theory (LCT) for semiflexible linear telechelic melts, developed in Paper I, is applied to examine the influence of chain stiffness on the average degree of self-assembly and the basic thermodynamic properties of linear telechelic polymer melts. Our calculations imply that chain stiffness promotes self-assembly of linear telechelic polymer melts that assemble on cooling when either polymer volume fraction ϕ or temperature T is high, but opposes self-assembly when both ϕ and T are sufficiently low. This allows us to identify a boundary line in the ϕ-T plane that separates two regions of qualitatively different influence of chain stiffness on self-assembly. The enthalpy and entropy of self-assembly are usually treated as adjustable parameters in classical Flory-Huggins type theories for the equilibrium self-assembly of polymers, but they are demonstrated here to strongly depend on chain stiffness. Moreover, illustrative calculations for the dependence of the entropy density of linear telechelic polymer melts on chain stiffness demonstrate the importance of including semiflexibility within the LCT when exploring the nature of glass formation in models of linear telechelic polymer melts.

  19. Lattice model of linear telechelic polymer melts. II. Influence of chain stiffness on basic thermodynamic properties

    Science.gov (United States)

    Xu, Wen-Sheng; Freed, Karl F.

    2015-07-01

    The lattice cluster theory (LCT) for semiflexible linear telechelic melts, developed in Paper I, is applied to examine the influence of chain stiffness on the average degree of self-assembly and the basic thermodynamic properties of linear telechelic polymer melts. Our calculations imply that chain stiffness promotes self-assembly of linear telechelic polymer melts that assemble on cooling when either polymer volume fraction ϕ or temperature T is high, but opposes self-assembly when both ϕ and T are sufficiently low. This allows us to identify a boundary line in the ϕ-T plane that separates two regions of qualitatively different influence of chain stiffness on self-assembly. The enthalpy and entropy of self-assembly are usually treated as adjustable parameters in classical Flory-Huggins type theories for the equilibrium self-assembly of polymers, but they are demonstrated here to strongly depend on chain stiffness. Moreover, illustrative calculations for the dependence of the entropy density of linear telechelic polymer melts on chain stiffness demonstrate the importance of including semiflexibility within the LCT when exploring the nature of glass formation in models of linear telechelic polymer melts.

  20. Charge states and lattice sites of dilute implanted Sn in ZnO

    Science.gov (United States)

    Mølholt, T. E.; Gunnlaugsson, H. P.; Johnston, K.; Mantovan, R.; Röder, J.; Adoons, V.; Mokhles Gerami, A.; Masenda, H.; Matveyev, Y. A.; Ncube, M.; Unzueta, I.; Bharuth-Ram, K.; Gislason, H. P.; Krastev, P.; Langouche, G.; Naidoo, D.; Ólafsson, S.; Zenkevich, A.; ISOLDE Collaboration

    2017-04-01

    The common charge states of Sn are 2+  and 4+. While charge neutrality considerations favour 2+  to be the natural charge state of Sn in ZnO, there are several reports suggesting the 4+  state instead. In order to investigate the charge states, lattice sites, and the effect of the ion implantation process of dilute Sn atoms in ZnO, we have performed 119Sn emission Mössbauer spectroscopy on ZnO single crystal samples following ion implantation of radioactive 119In (T ½  =  2.4 min) at temperatures between 96 K and 762 K. Complementary perturbed angular correlation measurements on 111mCd implanted ZnO were also conducted. Our results show that the 2+  state is the natural charge state for Sn in defect free ZnO and that the 4+  charge state is stabilized by acceptor defects created in the implantation process.

  1. Charge Transport in Carbon Nanotubes-Polymer Composite Photovoltaic Cells

    Directory of Open Access Journals (Sweden)

    Joel Davenas

    2009-06-01

    Full Text Available We investigate the dark and illuminated current density-voltage (J/V characteristics of poly(2-methoxy-5-(2’-ethylhexyloxy1-4-phenylenevinylene (MEH-PPV/single-walled carbon nanotubes (SWNTs composite photovoltaic cells. Using an exponential band tail model, the conduction mechanism has been analysed for polymer only devices and composite devices, in terms of space charge limited current (SCLC conduction mechanism, where we determine the power parameters and the threshold voltages. Elaborated devices for MEH-PPV:SWNTs (1:1 composites showed a photoresponse with an open-circuit voltage Voc of 0.4 V, a short-circuit current density JSC of 1 µA/cm² and a fill factor FF of 43%. We have modelised the organic photovoltaic devices with an equivalent circuit, where we calculated the series and shunt resistances.

  2. Bending stiff charged polymers: The electrostatic persistence length

    Science.gov (United States)

    Trizac, Emmanuel; Shen, Tongye

    2016-10-01

    Many charged polymers, including nucleic acids, are locally stiff. Their bending rigidity —quantified by the persistence length— depends crucially on Coulombic features, such as the ionic strength of the solution which offers a convenient experimental route for tuning the rigidity. While the classic Odijk-Skolnick-Fixman treatment fails for realistic parameter values, we derive a simple analytical formula for the electrostatic persistence length. It is shown to be in remarkable agreement with numerically obtained Poisson-Boltzmann theory results, thereby fully accounting for non-linearities, among which counter-ion condensation effects. Specified to double-stranded DNA, our work reveals that the widely used bare persistence length of 500 Å is overestimated by some 20%.

  3. Possible Global Minimum Lattice Configurations for Thomson`s Problem of Charges on a Sphere

    Energy Technology Data Exchange (ETDEWEB)

    Altschuler, E.L.; Tipton, R.; Dowla, F. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States); Williams, T.J. [Los Alamos National Laboratory, MS B256, Los Alamos, New Mexico 87545 (United States); Ratner, E.R. [Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Stong, R. [Department of Mathematics, Rice University, Houston, Texas 77004 (United States); Wooten, F. [Department of Applied Science, University of California Davis/Livermore, P.O. Box 808, Livermore, California 94551 (United States)

    1997-04-01

    What configuration of N point charges on a conducting sphere minimizes the Coulombic energy? J.J. Thomson posed this question in 1904. For N{le}112, numerical methods have found apparent global minimum-energy configurations; but the number of local minima appears to grow exponentially with N, making many such methods impractical. Here we describe a topological/numerical procedure that we believe gives the global energy minimum lattice configuration for N of the form N=10(m{sup 2}+n{sup 2}+mn)+2 (m, n positive integers). For those N with more than one lattice, we give a rule to choose the minimum one. {copyright} {ital 1997} {ital The American Physical Society}

  4. Systematic studies on the effect of linear lattice optics for space-charge limited beams

    CERN Document Server

    Fitterer, M; Molodozhentsev, A; Müller, A S

    2015-01-01

    The HL-LHC (High Luminosity LHC) project aims to an increase of the luminosity of the LHC by a factor of 10. In order to realize this ambitious goal, the LHC itself has to undergo a major upgrade accompanied by an extensive upgrade of the complete injector complex referred to as LHC injector upgrade (LIU). In the framework of the LIU project, a new rapid cycling synchrotron (RCS) as an alternative to the energy upgrade of the existing PS Booster has been proposed. Motivated by the optics studies conducted for this RCS, the more general question of the influence of the linear optics on the machine performance has been raised. In this paper, we want to investigate this question by comparing different lattices with the final aim of identifying lattice characteristics advantageous under strong space-charge effects.

  5. Adiabatic bond charge model for lattice dynamics of ternary chalcopyrite semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Guerel, T.; Eryigit, R. [Department of Physics, Abant Izzet Baysal University, Bolu, 14280 (Turkey)

    2006-01-01

    The adiabatic bond charge model of Rustagi and Weber is extended to study lattice dynamical properties of ternary chalcopyrite semiconductors AgGaS{sub 2}, AgGaSe{sub 2}, CuInS{sub 2}, CuInSe{sub 2}, CuGaS{sub 2}, CuGaSe{sub 2}, CuAlS{sub 2} and CuAlSe{sub 2}. The new model calculations agree well with the results of Raman/IR and neutron measurements of Brillouin zone center phonon frequencies for both low and high frequency modes which was difficult for other phenomenological lattice dynamical models. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Anharmonicity of lattice vibrations induced by charged nickel additions in A sup 2 B sup 6 semiconductors

    CERN Document Server

    Sokolov, V I; Shirokov, E A; Kislov, A N

    2002-01-01

    Paper presents the results of investigations into lattice vibrations induced by nickel impurities charged negatively as to the lattice in ZnSe:Ni, ZnO:Ni, ZnS:Ni, CdS:Ni semiconductors. To investigate into vibrations one applies a sensitive technique of field exciton-oscillation spectroscopy. One observes experimentally oscillating reiterations of the impurity exciton head line including the intensive peaks of combined repetitions up to the 8-th order. The experimental results are discussed on the basis of the model estimations of oscillations of a lattice with a charged impurity centre, as well as, on the ground of calculations for oscillations of monoatomic chain with high anharmonicity. Charged impurity centres are shown to induce new oscillations of lattice - impurity anharmonic modes

  7. Small interfering RNA delivery through positively charged polymer nanoparticles

    Science.gov (United States)

    Dragoni, Luca; Ferrari, Raffaele; Lupi, Monica; Cesana, Alberto; Falcetta, Francesca; Ubezio, Paolo; D'Incalci, Maurizio; Morbidelli, Massimo; Moscatelli, Davide

    2016-03-01

    Small interfering RNA (siRNA) is receiving increasing attention with regard to the treatment of many genetic diseases, both acquired and hereditary, such as cancer and diabetes. Being a high molecular weight (MW) polyanion, siRNA is not able to cross a cell membrane, and in addition it is unstable in physiological conditions. Accordingly, a biocompatible nanocarrier able to deliver siRNA into cells is needed. In this work, we synthesized biocompatible positively charged nanoparticles (NPs) following a two-step process that involves ring opening polymerization (ROP) and emulsion free radical polymerization (EFRP). Firstly, we proved the possibility of fine tuning the NPs’ characteristics (e.g. size and surface charge) by changing the synthetic process parameters. Then the capability in loading and delivering undamaged siRNA into a cancer cell cytoplasm has been shown. This latter process occurs through the biodegradation of the polymer constituting the NPs, whose kinetics can be tuned by adjusting the polymer’s MW. Finally, the ability of NPs to carry siRNA inside the cells in order to inhibit their target gene has been demonstrated using green flourescent protein positive cells.

  8. Chiral Soliton Lattice and Charged Pion Condensation in Strong Magnetic Fields

    CERN Document Server

    Brauner, Tomas

    2016-01-01

    The Chiral Soliton Lattice (CSL) is a state with a periodic array of topological solitons that spontaneously breaks parity and translational symmetries. Such a state is known to appear in chiral magnets. We show that CSL also appears as a ground state of quantum chromodynamics at nonzero chemical potential in a magnetic field. By analyzing the fluctuations of the CSL, we furthermore demonstrate that in strong but achievable magnetic fields, charged pions undergo Bose-Einstein condensation. Our results, based on a systematic low-energy effective theory, are model-independent and fully analytic.

  9. Fractional charge separation in the hard-core Bose Hubbard Model on the Kagome Lattice

    Science.gov (United States)

    Zhang, Xue Feng; Eggert, Sebastian

    2013-03-01

    We consider the hard core Bose Hubbard Model on a Kagome lattice with fixed (open) boundary conditions on two edges. We find that the fixed boundary conditions lift the degeneracy and freeze the system at 1/3 and 2/3 filling at small hopping. At larger hopping strengths, fractional charges spontaneously separate and are free to move to the edges of the system, which leads to a novel compressible phase with solid order. The compressibility is due to excitations on the edge which display a chrial symmetry breaking that is reminiscent of the quantum Hall effect. Large scale Monte Carlo simulations confirm the analytical calculations.

  10. Nucleon Scalar and Tensor Charges from Lattice QCD with Light Wilson Quarks

    CERN Document Server

    Green, J R; Pochinsky, A V; Syritsyn, S N; Engelhardt, M; Krieg, S

    2012-01-01

    We present 2+1 flavor Lattice QCD calculations of the nucleon scalar and tensor charges. Using the BMW clover-improved Wilson action with pion masses between 150 and 350 MeV and three source-sink separations between 0.9 and 1.4 fm, we achieve good control over excited-state contamination and extrapolation to the physical pion mass. As a consistency check, we also present results from calculations using unitary domain wall fermions with pion masses between 300 and 400 MeV, and using domain wall valence quarks and staggered sea quarks with pion masses between 300 and 600 MeV.

  11. Chiral soliton lattice and charged pion condensation in strong magnetic fields

    Science.gov (United States)

    Brauner, Tomáš; Yamamoto, Naoki

    2017-04-01

    The Chiral Soliton Lattice (CSL) is a state with a periodic array of topological solitons that spontaneously breaks parity and translational symmetries. Such a state is known to appear in chiral magnets. We show that CSL also appears as a ground state of quantum chromodynamics at nonzero chemical potential in a magnetic field. By analyzing the fluctuations of the CSL, we furthermore demonstrate that in strong but achievable magnetic fields, charged pions undergo Bose-Einstein condensation. Our results, based on a systematic low-energy effective theory, are model-independent and fully analytic.

  12. How disorder controls the kinetics of triplet charge recombination in semiconducting organic polymer photovoltaics.

    Science.gov (United States)

    Bittner, Eric R; Lankevich, Vladimir; Gélinas, Simon; Rao, Akshay; Ginger, David A; Friend, Richard H

    2014-10-14

    Recent experiments by Rao et al. (Nature, 2013, 500, 435-439) indicate that recombination of triplet charge-separated states is suppressed in organic polymer-fullerene based bulk-heterojunction (BHJ) photovoltaic cells exhibiting a high degree of crystallinity in the fullerene phase relative to systems with more disorder. In this paper, we use a series of Frenkel-exciton lattice models to rationalize these results in terms of wave-function localization, interface geometry, and density of states. In one-dimensional co-linear and co-facial models of the interface, increasing local energetic disorder in one phase localizes the interfacial triplet charge-transfer ((3)CT) states and increases the rate at which these states relax to form lower-energy triplet excitons. In two dimensional BHJ models, energetic disorder within the fullerene phase plays little role in further localizing states pinned to the interface. However, inhomogeneous broadening introduces strong coupling between the interfacial (3)CT and nearby fullerene triplet excitons and can enhance the decay of these states in systems with higher degrees of energetic disorder.

  13. Efficient barrier for charge injection in polyethylene by silver nanoparticles/plasma polymer stack

    Energy Technology Data Exchange (ETDEWEB)

    Milliere, L. [LAPLACE (Laboratoire Plasma et Conversion d' Energie), Université de Toulouse, UPS, INPT, 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France); Makasheva, K., E-mail: kremena.makasheva@laplace.univ-tlse.fr; Laurent, C.; Despax, B.; Teyssedre, G. [LAPLACE (Laboratoire Plasma et Conversion d' Energie), Université de Toulouse, UPS, INPT, 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France); CNRS, LAPLACE, F-31062 Toulouse (France)

    2014-09-22

    Charge injection from a metal/insulator contact is a process promoting the formation of space charge in polymeric insulation largely used in thick layers in high voltage equipment. The internal charge perturbs the field distribution and can lead to catastrophic failure either through its electrostatic effects or through energetic processes initiated under charge recombination and/or hot electrons effects. Injection is still ill-described in polymeric insulation due to the complexity of the contact between the polymer chains and the electrodes. Barrier heights derived from the metal work function and the polymer electronic affinity do not provide a good description of the measurements [Taleb et al., IEEE Trans. Dielectr. Electr. Insul. 20, 311–320 (2013)]. Considering the difficulty to describe the contact properties and the need to prevent charge injection in polymers for high voltage applications, we developed an alternative approach by tailoring the interface properties by the silver nanoparticles (AgNPs)/plasma polymer stack, deposited on the polymer film. Due to their small size, the AgNPs, covered by a very thin film of plasma polymer, act as deep traps for the injected charges thereby stabilizing the interface from the point of view of charge injection. After a quick description of the method for elaborating the nanostructured layer near the contact, it is demonstrated how the AgNPs/plasma polymer stack effectively prevents, in a spectacular way, the formation of bulk space charge.

  14. Efficient barrier for charge injection in polyethylene by silver nanoparticles/plasma polymer stack

    Science.gov (United States)

    Milliere, L.; Makasheva, K.; Laurent, C.; Despax, B.; Teyssedre, G.

    2014-09-01

    Charge injection from a metal/insulator contact is a process promoting the formation of space charge in polymeric insulation largely used in thick layers in high voltage equipment. The internal charge perturbs the field distribution and can lead to catastrophic failure either through its electrostatic effects or through energetic processes initiated under charge recombination and/or hot electrons effects. Injection is still ill-described in polymeric insulation due to the complexity of the contact between the polymer chains and the electrodes. Barrier heights derived from the metal work function and the polymer electronic affinity do not provide a good description of the measurements [Taleb et al., IEEE Trans. Dielectr. Electr. Insul. 20, 311-320 (2013)]. Considering the difficulty to describe the contact properties and the need to prevent charge injection in polymers for high voltage applications, we developed an alternative approach by tailoring the interface properties by the silver nanoparticles (AgNPs)/plasma polymer stack, deposited on the polymer film. Due to their small size, the AgNPs, covered by a very thin film of plasma polymer, act as deep traps for the injected charges thereby stabilizing the interface from the point of view of charge injection. After a quick description of the method for elaborating the nanostructured layer near the contact, it is demonstrated how the AgNPs/plasma polymer stack effectively prevents, in a spectacular way, the formation of bulk space charge.

  15. Charge generation in polymer-fullerene bulk-heterojunction solar cells

    OpenAIRE

    Gao, Feng; Inganäs, Olle

    2014-01-01

    Charge generation in organic solar cells is a fundamental yet heavily debated issue. This article gives a balanced review of different mechanisms proposed to explain efficient charge generation in polymer-fullerene bulk-heterojunction solar cells. We discuss the effect of charge-transfer states, excess energy, external electric field, temperature, disorder of the materials, and delocalisation of the charge carriers on charge generation. Although a general consensus has not been reached yet, r...

  16. Adsorption of charged and neutral polymer chains on silica surfaces: The role of electrostatics, volume exclusion, and hydrogen bonding

    Science.gov (United States)

    Spruijt, Evan; Biesheuvel, P. M.; de Vos, Wiebe M.

    2015-01-01

    We develop an off-lattice (continuum) model to describe the adsorption of neutral polymer chains and polyelectrolytes to surfaces. Our continuum description allows taking excluded volume interactions between polymer chains and ions directly into account. To implement those interactions, we use a modified hard-sphere equation of state, adapted for mixtures of connected beads. Our model is applicable to neutral, charged, and ionizable surfaces and polymer chains alike and accounts for polarizability effects of the adsorbed layer and chemical interactions between polymer chains and the surface. We compare our model predictions to data of a classical system for polymer adsorption: neutral poly(N -vinylpyrrolidone) (PVP) on silica surfaces. The model shows that PVP adsorption on silica is driven by surface hydrogen bonding with an effective maximum binding energy of about 1.3 kBT per PVP segment at low p H . As the p H increases, the Si-OH groups become increasingly dissociated, leading to a lower capacity for H bonding and simultaneous counterion accumulation and volume exclusion close to the surface. Together these effects result in a characteristic adsorption isotherm, with the adsorbed amount dropping sharply at a critical p H . Using this model for adsorption data on silica surfaces cleaned by either a piranha solution or an O2 plasma, we find that the former have a significantly higher density of silanol groups.

  17. Unbiased charge oscillations in DNA monomer-polymers and dimer-polymers

    CERN Document Server

    Lambropoulos, Konstantinos; Morphis, Andreas; Kaklamanis, Konstantinos; Theodorakou, Marina; Simserides, Constantinos

    2015-01-01

    We call {\\it monomer} a B-DNA base-pair and examine, analytically and numerically, electron or hole oscillations in monomer- and dimer-polymers, i.e., periodic sequences with repetition unit made of one or two monomers. We employ a tight-binding (TB) approach at the base-pair level to readily determine the spatiotemporal evolution of a single extra carrier along a $N$ base-pair polymer. We study HOMO and LUMO eigenspectra as well as the mean over time probabilities to find the carrier at a particular monomer. We use the pure mean transfer rate $k$ to evaluate the easiness of charge transfer. The inverse decay length $\\beta$ for exponential fits $k(d)$, where $d$ is the charge transfer distance, and the exponent $\\eta$ for power law fits $k(N)$ are computed; generally power law fits are better. We illustrate that increasing the number of different parameters involved in the TB description, the fall of $k(d)$ or $k(N)$ becomes steeper and show the range covered by $\\beta$ and $\\eta$. Finally, both for the time-...

  18. Iso-vector and iso-scalar tensor charges of the nucleon from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Gupta, Rajan; Yoon, Boram [Los Alamos National Laboratory, NM (United States). Theoretical Div. T-2; Cohen, Saul D. [Washington Univ., Seattle, WA (United States). Inst. for Nuclear Theory; Joseph, Anosh [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Lin, Huey-Wen [California Univ., Berkeley, CA (United States). Dept. of Physics; Collaboration: PNDME Collaboration

    2015-07-15

    We present results for the iso-vector and flavor diagonal tensor charges g{sup u-d}{sub T}, g{sup u}{sub T}, g{sup d}{sub T}, and g{sup s}{sub T} needed to probe novel tensor interactions at the TeV scale in neutron and nuclear β-decays and the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice QCD calculations were done using nine ensembles of gauge configurations generated by the MILC collaboration using the HISQ action with 2+1+1 dynamical flavors. These ensembles span three lattice spacings a∼0.06, 0.09 and 0.12 fm and three quark masses corresponding to the pion masses M{sub π}∼130, 220 and 310 MeV. Using estimates from these ensembles, we quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, volume and light quark masses for the connected contributions. The final estimates of the connected nucleon (proton) tensor charge for the iso-vector combination is g{sup u-d}{sub T}=1.020(76) in the MS scheme at 2 GeV. The additional disconnected quark loop contributions needed for the flavor-diagonal matrix elements are calculated using a stochastic estimator employing the truncated solver method with the all-mode-averaging technique. We find that the size of the disconnected contribution is smaller than the statistical error in the connected contribution. This allows us to bound the disconnected contribution and include it as an additional uncertainty in the flavor-diagonal charges. After a continuum extrapolation, we find g{sup u}{sub T}=0.774(66), g{sup d}{sub T}=-0.233(28) and g{sup u+d}{sub T}=0.541(67). The strangeness tensor charge, that can make a significant contribution to the neutron EDM due to the large ratio m{sub s}/m{sub u,d}, is g{sup s}{sub T}=0.008(9) in the continuum limit.

  19. Structure and Morphology Control in Thin Films of Conjugated Polymers for an Improved Charge Transport

    Directory of Open Access Journals (Sweden)

    Haiyang Wang

    2013-11-01

    Full Text Available The morphological and structural features of the conjugated polymer films play an important role in the charge transport and the final performance of organic optoelectronics devices [such as organic thin-film transistor (OTFT and organic photovoltaic cell (OPV, etc.] in terms of crystallinity, packing of polymer chains and connection between crystal domains. This review will discuss how the conjugated polymer solidify into, for instance, thin-film structures, and how to control the molecular arrangement of such functional polymer architectures by controlling the polymer chain rigidity, polymer solution aggregation, suitable processing procedures, etc. These basic elements in intrinsic properties and processing strategy described here would be helpful to understand the correlation between morphology and charge transport properties and guide the preparation of efficient functional conjugated polymer films correspondingly.

  20. Foaming and foam stability for mixed polymer-surfactant solutions: effects of surfactant type and polymer charge.

    Science.gov (United States)

    Petkova, R; Tcholakova, S; Denkov, N D

    2012-03-20

    Solutions of surfactant-polymer mixtures often exhibit different foaming properties, compared to the solutions of the individual components, due to the strong tendency for formation of polymer-surfactant complexes in the bulk and on the surface of the mixed solutions. A generally shared view in the literature is that electrostatic interactions govern the formation of these complexes, for example between anionic surfactants and cationic polymers. In this study we combine foam tests with model experiments to evaluate and explain the effect of several polymer-surfactant mixtures on the foaminess and foam stability of the respective solutions. Anionic, cationic, and nonionic surfactants (SDS, C(12)TAB, and C(12)EO(23)) were studied to clarify the role of surfactant charge. Highly hydrophilic cationic and nonionic polymers (polyvinylamine and polyvinylformamide, respectivey) were chosen to eliminate the (more trivial) effect of direct hydrophobic interactions between the surfactant tails and the hydrophobic regions on the polymer chains. Our experiments showed clearly that the presence of opposite charges is not a necessary condition for boosting the foaminess and foam stability in the surfactant-polymer mixtures studied. Clear foam boosting (synergistic) effects were observed in the mixtures of cationic surfactant and cationic polymer, cationic surfactant and nonionic polymer, and anionic surfactant and nonionic polymer. The mixtures of anionic surfactant and cationic polymer showed improved foam stability, however, the foaminess was strongly reduced, as compared to the surfactant solutions without polymer. No significant synergistic or antagonistic effects were observed for the mixture of nonionic surfactant (with low critical micelle concentration) and nonionic polymer. The results from the model experiments allowed us to explain the observed trends by the different adsorption dynamics and complex formation pattern in the systems studied.

  1. Charge photogeneration and transport in side-chain carbazole polymers and co-polymers

    KAUST Repository

    Li, Huawei

    2011-07-01

    The photoconductivity, hole mobility and charge photogeneration efficiency of a series of side-chain carbazole homopolymers and copolymers (with azo side-chains) have been investigated. Cyclic voltammetry measurement of frontier orbitals energies show that the HOMO energy is determined by the nature and the position of attachment of the linker between the main chain and the carbazole, the azo-moiety being not relevant in this respect. Hole mobility is not influenced by the HOMO energy but seems to depend on the degree of conformational mobility of the side-chains, reaching values of the order of 10-3cm2V-1s-1 in the best cases. The HOMO energy is instead extremely important when considering photogeneration efficiency, that can change by 10 orders of magnitude depending on the density of the carbazole side-chains in co-polymers and on the linker nature and attachment position. © 2011 Elsevier B.V. All rights reserved.

  2. Second-Order Phase Transition in the Two-Dimensional Classical Lattice Coulomb Gas of Half-Integer Charges

    Institute of Scientific and Technical Information of China (English)

    罗孟波; 陈庆虎; 许祝安; 焦正宽

    2001-01-01

    The second-order phase transition in the two-dimensional (2D) classical Coulomb gas of half-integer charges on a square lattice is investigated by using Monte Carlo simulations. Based on the finite-size scaling analysis,we estimate the second-order phase transition temperature Tc and the static critical exponents β and v with a new numerical analysis method. More precise critical temperature Tc = 0.1311(2) and critical exponents β/ν = 0.1152(12) and ν = 0.857(15) are obtained. The estimated value of ν indicates that the charge lattice melting transition is different from the pure 2D Ising transition.

  3. Control of surface charges by radicals as a principle of antistatic polymers protecting electronic circuitry.

    Science.gov (United States)

    Baytekin, H Tarik; Baytekin, Bilge; Hermans, Thomas M; Kowalczyk, Bartlomiej; Grzybowski, Bartosz A

    2013-09-20

    Even minute quantities of electric charge accumulating on polymer surfaces can cause shocks, explosions, and multibillion-dollar losses to electronic circuitry. This paper demonstrates that to remove static electricity, it is not at all necessary to "target" the charges themselves. Instead, the way to discharge a polymer is to remove radicals from its surface. These radicals colocalize with and stabilize the charges; when they are scavenged, the surfaces discharge rapidly. This radical-charge interplay allows for controlling static electricity by doping common polymers with small amounts of radical-scavenging molecules, including the familiar vitamin E. The effectiveness of this approach is demonstrated by rendering common polymers dust-mitigating and also by using them as coatings that prevent the failure of electronic circuitry.

  4. Direct observation of ultrafast long-range charge separation at polymer:fullerene heterojunctions

    Science.gov (United States)

    Silva, Carlos

    2014-03-01

    In polymeric semiconductors, charge carriers are polarons, which means that the excess charge deforms the molecular structure of the polymer chain that hosts it. This effect results in distinctive signatures in the vibrational modes of the polymer. We probe polaron photogeneration dynamics at polymer:fullerene heterojunctions by monitoring its time-resolved resonance-Raman spectrum following ultrafast photoexcitation. We conclude that polarons emerge within 200 fs, which is nearly two orders of magnitude faster than exciton localisation in the neat polymer film. Surprisingly, further vibrational evolution on polarons is not significantly different from that in equilibrium. This suggests that charges are free from their mutual Coulomb potential, under which vibrational dynamics would report charge-pair relaxation. Our work addresses current debates on the photocarrier generation mechanism at organic semiconductor heterojunctions, and is, to our knowledge, the first direct probe of molecular conformation dynamics during this fundamentally important process in these materials.

  5. Direct observation of ultrafast long-range charge separation at polymer-fullerene heterojunctions

    Science.gov (United States)

    Provencher, Françoise; Bérubé, Nicolas; Parker, Anthony W.; Greetham, Gregory M.; Towrie, Michael; Hellmann, Christoph; Côté, Michel; Stingelin, Natalie; Silva, Carlos; Hayes, Sophia C.

    2014-07-01

    In polymeric semiconductors, charge carriers are polarons, which means that the excess charge deforms the molecular structure of the polymer chain that hosts it. This results in distinctive signatures in the vibrational modes of the polymer. Here, we probe polaron photogeneration dynamics at polymer:fullerene heterojunctions by monitoring its time-resolved resonance-Raman spectrum following ultrafast photoexcitation. We conclude that polarons emerge within 300 fs. Surprisingly, further structural evolution on ≲50-ps timescales is modest, indicating that the polymer conformation hosting nascent polarons is not significantly different from that near equilibrium. We interpret this as suggestive that charges are free from their mutual Coulomb potential because we would expect rich vibrational dynamics associated with charge-pair relaxation. We address current debates on the photocarrier generation mechanism at molecular heterojunctions, and our work is, to our knowledge, the first direct probe of molecular conformation dynamics during this fundamentally important process in these materials.

  6. Quantum spin Hall effect and spin-charge separation in a kagome lattice

    Energy Technology Data Exchange (ETDEWEB)

    Wang Zhigang; Zhang Ping, E-mail: zhang_ping@iapcm.ac.c [LCP, Institute of Applied Physics and Computational Mathematics, PO Box 8009, Beijing 100088 (China)

    2010-04-15

    A two-dimensional kagome lattice is theoretically investigated within a simple tight-binding model, which includes the nearest-neighbor hopping term and the intrinsic spin-orbit interaction between the next nearest neighbors. By using the topological winding properties of the spin-edge states on the complex-energy Riemann surface, the spin Hall conductance is obtained to be quantized as -e/2{pi} (e/2{pi}) in insulating phases. This result is consistent with the numerical linear-response calculation and the Z{sub 2} topological invariance analysis. When the sample boundaries are connected in twist, by which two defects with {pi} flux are introduced, we obtain the spin-charge separated solitons at 1/3 (or 2/3) filling.

  7. Topological phase transition and charge pumping in a one-dimensional periodically driven optical lattice

    Science.gov (United States)

    Xu, Zhihao; Zhang, Yunbo; Chen, Shu

    2017-07-01

    Experimental realizations of topological quantum systems and detections of topological invariants in ultracold atomic systems have been a greatly attractive topic. In this work, we propose a scheme to realize topologically different phases in a bichromatic optical lattice subjected to a periodically driven tilt harmonic oscillation, which can be effectively described by a superlattice model with tunable long-range hopping processes. By tuning the ratio of nearest-neighbor (NN) and next-nearest-neighbor (NNN) hopping amplitudes, the system undergoes a topological phase transition accompanied by the change of topological numbers of the lowest band from -1 to 2. Using a slowly time-periodic modulation, the system emerges distinct quantized topological pumped charges (TPCs) of atoms in the filled band for different topological phases. Our scheme is realizable in current cold atomic technique.

  8. Lattice Thermal Conductivity of Superlattices from an Adiabatic Bond Charge Model

    Science.gov (United States)

    Ward, Alistair; Broido, David

    2007-03-01

    The adiabatic bond charge model (ABCM) has successfully rendered phonon dispersions of a host of bulk semiconductors [1,2] and has also been used to calculate the phonon dispersions in quantum well superlattices [3]. We have developed an ABCM for superlattices and combined it with a symmetry-based representation of the anharmonic interatomic forces to calculate the lattice thermal conductivity of short-period superlattices, using an iterative solution to the Boltzmann-Peierls equation [4]. We compare our ABCM results with those obtained from some commonly used models for the interatomic forces in semiconductors to assess the importance of accurate descriptions of the phonon dispersions in thermal conductivity calculations. [1] W. Weber, Physical Review B 15, 4789 (1977). [2] K. C. Rustagi and W. Weber, Solid State Communications 18, 673 (1976). [3] S. K. Yip and Y. C. Chang, Physical Review B 30 7037 (1984). [4] D. A. Broido, A. Ward, and N. Mingo, Physical Review B 72, 014308 (2005).

  9. Structure and interaction in the polymer-dependent reentrant phase behavior of a charged nanoparticle solution.

    Science.gov (United States)

    Kumar, Sugam; Ray, D; Aswal, V K; Kohlbrecher, J

    2014-10-01

    Small-angle neutron scattering (SANS) studies have been carried out to examine the evolution of interaction and structure in a nanoparticle (silica)-polymer (polyethylene glycol) system. The nanoparticle-polymer solution interestingly shows a reentrant phase behavior where the one-phase charged stabilized nanoparticles go through a two-phase system (nanoparticle aggregation) and back to one-phase as a function of polymer concentration. Such phase behavior arises because of the nonadsorption of polymer on nanoparticles and is governed by the interplay of polymer-induced attractive depletion with repulsive nanoparticle-nanoparticle electrostatic and polymer-polymer interactions in different polymer concentration regimes. At low polymer concentrations, the electrostatic repulsion dominates over the depletion attraction. However, the increase in polymer concentration enhances the depletion attraction to give rise to the nanoparticle aggregation in the two-phase system. Further, the polymer-polymer repulsion at high polymer concentrations is believed to be responsible for the reentrance to one-phase behavior. The SANS data in polymer contrast-matched conditions have been modeled by a two-Yukawa potential accounting for both repulsive and attractive parts of total interaction potential between nanoparticles. Both of these interactions (repulsive and attractive) are found to be long range. The magnitude and the range of the depletion interaction increase with the polymer concentration leading to nanoparticle clustering. At higher polymer concentrations, the increased polymer-polymer repulsion reduces the depletion interaction leading to reentrant phase behavior. The nanoparticle clusters in the two-phase system are characterized by the surface fractal with simple cubic packing of nanoparticles within the clusters. The effect of varying ionic strength and polymer size in tuning the interaction has also been examined.

  10. Two phase flow simulation in a channel of a polymer electrolyte membrane fuel cell using the lattice Boltzmann method

    OpenAIRE

    Ben Salah, Yasser; Tabe, Yutaka; Chikahisa, Takemi

    2012-01-01

    Water management in polymer electrolyte (PEM) fuel cells is important for fuel cell performance and durability. Numerical simulations using the lattice Boltzmann method (LBM) are developed to elucidate the dynamic behavior of condensed water and gas flows in a polymer electrolyte membrane (PEM) fuel cell gas channel. A scheme for two-phase flow with large density differences was applied to establish the optimum gas channel design for different gas channel heights, droplet positions, and gas c...

  11. Gel formation in systems composed of drug containing catanionic vesicles and oppositely charged hydrophobically modified polymer.

    Science.gov (United States)

    Dew, Noel; Edwards, Katarina; Edsman, Katarina

    2009-05-01

    The aim of this study was to explore if mixtures of drug containing catanionic vesicles and polymers give rise to gel formation, and if so, if drug release from these gels could be prolonged. Catanionic vesicles formed from the drug substances alprenolol or tetracaine, and the oppositely charged surfactant sodium dodecyl sulphate were mixed with polymers. Three polymers with different properties were employed: one bearing hydrophobic modifications, one positively charged and one positively charged polymer bearing hydrophobic modifications. The structure of the vesicles before and after addition of polymer was investigated by using cryo-TEM. Gel formation was confirmed by using rheological measurements. Drug release was studied using a modified USP paddle method. Gels were observed to form only in the case when catanionic vesicles, most likely with a net negative charge, were mixed with positively charged polymer bearing lipophilic modifications. The release of drug substance from these systems, where the vesicles are not trapped within the gel but constitute a founding part of it, could be significantly prolonged. The drug release rate was found to depend on vesicle concentration to a higher extent than on polymer concentration.

  12. Structure and Morphology Control in Thin Films of Conjugated Polymers for an Improved Charge Transport

    OpenAIRE

    Haiyang Wang; Yaozhuo Xu; Xinhong Yu; Rubo Xing; Jiangang Liu; Yanchun Han

    2013-01-01

    The morphological and structural features of the conjugated polymer films play an important role in the charge transport and the final performance of organic optoelectronics devices [such as organic thin-film transistor (OTFT) and organic photovoltaic cell (OPV), etc.] in terms of crystallinity, packing of polymer chains and connection between crystal domains. This review will discuss how the conjugated polymer solidify into, for instance, thin-film structures, and how to control the molecula...

  13. Structure and Morphology Control in Thin Films of Conjugated Polymers for an Improved Charge Transport

    OpenAIRE

    Haiyang Wang; Yaozhuo Xu; Xinhong Yu; Rubo Xing; Jiangang Liu; Yanchun Han

    2013-01-01

    The morphological and structural features of the conjugated polymer films play an important role in the charge transport and the final performance of organic optoelectronics devices [such as organic thin-film transistor (OTFT) and organic photovoltaic cell (OPV), etc.] in terms of crystallinity, packing of polymer chains and connection between crystal domains. This review will discuss how the conjugated polymer solidify into, for instance, thin-film structures, and how to control the molecula...

  14. Energy and charge control in mass spectrometry of synthetic polymers

    NARCIS (Netherlands)

    Nasioudis, A.

    2011-01-01

    Synthetic polymers are the products of humans’ attempts to imitate nature’s gigantic molecular chain architectures. The extended variety of building blocks and reaction mechanisms resulted in a plethora of different polymeric architectures. The biggest challenge for polymer chemists is to develop an

  15. Ultrafast Charge Separation in Low Band-Gap Polymer Blend for Photovoltaics

    Directory of Open Access Journals (Sweden)

    Egelhaaf Hans-J.

    2013-03-01

    Full Text Available We track ultrafast charge dissociation in a particularly promising low-band-gap- polymer:fullerene blend for organic photovoltaics. Impulsive photoexcitation with excess energy leads to a 30-fs formation of an hot charge transfer state, precursor of free carriers.

  16. Thermally Induced Charge Reversal of Layer-by-Layer Assembled Single-Component Polymer Films.

    Science.gov (United States)

    Richardson, Joseph J; Tardy, Blaise L; Ejima, Hirotaka; Guo, Junling; Cui, Jiwei; Liang, Kang; Choi, Gwan H; Yoo, Pil J; De Geest, Bruno G; Caruso, Frank

    2016-03-23

    Temperature can be harnessed to engineer unique properties for materials useful in various contexts and has been shown to affect the layer-by-layer (LbL) assembly of polymer thin films and cause physical changes in preassembled polymer thin films. Herein we demonstrate that exposure to relatively low temperatures (≤ 100 °C) can induce physicochemical changes in cationic polymer thin films. The surface charge of polymer films containing primary and secondary amines reverses after heating (from positive to negative), and different characterization techniques are used to show that the change in surface charge is related to oxidation of the polymer that specifically occurs in the thin film state. This charge reversal allows for single-polymer LbL assembly to be performed with poly(allylamine) hydrochloride (PAH) through alternating heat/deposition steps. Furthermore, the negative charge induced by heating reduces the fouling and cell-association of PAH-coated planar and particulate substrates, respectively. This study highlights a unique property of thin films which is relevant to LbL assembly and biofouling and is of interest for the future development of thin polymer films for biomedical systems.

  17. Role of Molecular Weight Distribution on Charge Transport in Semiconducting Polymers

    KAUST Repository

    Himmelberger, Scott

    2014-10-28

    © 2014 American Chemical Society. Model semiconducting polymer blends of well-controlled molecular weight distributions are fabricated and demonstrated to be a simple method to control intermolecular disorder without affecting intramolecular order or degree of aggregation. Mobility measurements exhibit that even small amounts of low molecular weight material are detrimental to charge transport. Trends in charge carrier mobility can be reproduced by a simple analytical model which indicates that carriers have no preference for high or low molecular weight chains and that charge transport is limited by interchain hopping. These results quantify the role of long polymer tie-chains and demonstrate the need for controlled polydispersity for achieving high carrier mobilities.

  18. A comparative simulation study on three lattice systems for the phase separation of polymer-dispersed liquid crystals

    Indian Academy of Sciences (India)

    Y J Jeon; M Jamil; Hyo-Dong Lee; J T Rhee

    2008-09-01

    This article reports a comparative study of the phase separation process in a polymer-dispersed liquid crystal, based on a Metropolis Monte Carlo simulation study of three lattice systems. We propose a model for the different processes occurring in the formation of polymer-dispersed liquid crystals (PDLCs). The mechanism of PDLC is studied as a function of quench temperature, concentration and degree of polymerization of liquid crystals and polymers. The obtained resultant phase diagrams of the three systems are approximated and compared with the Flory–Huggins theory, and show a good agreement. It has been observed in the simulation results that among all the three systems, the 40 × 40 × 40 lattice showed the most accurate, reliable and stable results.

  19. Exact Solution of an Extended Hubbard Model with Electron-Lattice Interaction for an Organic Ferromagnetic Polymer

    Institute of Scientific and Technical Information of China (English)

    王为忠; 姚凯伦

    2002-01-01

    Using an exact diagonalization method, we study an extended Hubbard model with an electron-lattice interaction for an organic ferromagnetic chain with radical coupling. The result shows that the ferromagnetic ground state originates from the antiferromagnetic correlation between adjoining sites, which is enhanced by the on-site e-e repulsion. The intersite e-e repulsion induces the inhomogeneous distribution of the charge density. The dimerization is decreased by the e-e interaction and the radical coupling. The electron--lattice interaction and the radical coupling can transfer the spin density and charge density between the main chain and the radicals.

  20. The Role of Polymer Fractionation in Energetic Losses and Charge Carrier Lifetimes of Polymer: Fullerene Solar Cells

    KAUST Repository

    Baran, Derya

    2015-08-10

    Non-radiative recombination reduces the open-circuit voltage relative to its theoretical limit and leads to reduced luminescence emission at a given excitation. Therefore it is possible to correlate changes in luminescence emission with changes in open-circuit voltage and in the charge carrier lifetime. Here we use luminescence studies combined with transient photovoltage and differential charging analyses to study the effect of polymer fractionation in indacenoedithiophene-co-benzothiadiazole (IDTBT):fullerene solar cells. In this system, polymer fractionation increases electroluminescence and reduces non-radiative recombination. High molecular weight and fractionated IDTBT polymers exhibit higher carrier lifetime-mobility product compared to their non-fractionated analogues, resulting in improved solar cell performance.

  1. Elucidation of charge storage characteristics of conducting polymer film using redox reaction

    CERN Document Server

    Contractor, Asfiya Q

    2013-01-01

    A general technique to investigate charge storage characteristics of conducting polymer films has been developed. A redox reaction is conducted on a polymer film on a rotating disk electrode under potentiostatic condition so that the rate of charging of the film equals the rate of removal of the charge by the reaction. In an experiment on polyaniline film deposited on platinum substrate, using Fe2+/Fe3+ in HCl as the redox system, the voltammogram shows five distinct linear segments (bands) with discontinuity in the slope at specific transition potentials. These bands are the same as those indicated by ESR/Raman spectroscopy with comparable transition potentials. From the dependence of the slopes of the bands on concentration of ferrous and ferric ions, it was possible to estimate the energies of the charge carrier in different bands. It is shown that the charge storage in the film is capacitive.

  2. Simulations of polymer brushes with charged end monomers under external electric fields

    Science.gov (United States)

    Ding, Huanda; Duan, Chao; Tong, Chaohui

    2017-01-01

    Using Langevin dynamics simulations, the response of neutral polymer brushes with charged terminal monomers to external electric fields has been investigated. The external electric field is equivalent to the field generated by the opposite surface charges on two parallel electrodes. The effects of charge valence of terminal monomers on the structure of double layers and overall charge balance near the two electrodes were examined. Using the charge density distributions obtained from simulations, the total electric field normal to the electrodes was calculated by numerically solving the Poisson equation. Under external electric fields, the total electric field across the two electrodes is highly non-uniform and in certain regions within the brush, the total electric field nearly vanishes. The probability distribution of electric force acting on one charged terminal monomer was obtained from simulations and how it affects the probability density distribution of terminal monomers was analyzed. The response of polymer brushes with charged terminal monomers to a strongly stretching external electric field was compared with that of uniformly charged polymer brushes.

  3. Electric Charge Accumulation in Polar and Non-Polar Polymers under Electron Beam Irradiation

    Science.gov (United States)

    Nagasawa, Kenichiro; Honjoh, Masato; Takada, Tatsuo; Miyake, Hiroaki; Tanaka, Yasuhiro

    The electric charge accumulation under an electron beam irradiation (40 keV and 60 keV) was measured by using the pressure wave propagation (PWP) method in the dielectric insulation materials, such as polar polymeric films (polycarbonate (PC), polyethylene-naphthalate (PEN), polyimide (PI), and polyethylene-terephthalate (PET)) and non-polar polymeric films (polystyrene (PS), polypropylene (PP), polyethylene (PE) and polytetrafluoroethylene (PTFE)). The PE and PTFE (non-polar polymers) showed the properties of large amount of electric charge accumulation over 50 C/m3 and long saturation time over 80 minutes. The PP and PS (non-polar polymer) showed the properties of middle amount of charge accumulation about 20 C/m3 and middle saturation time about 1 to 20 minutes. The PC, PEN, PI and PET (polar polymers) showed the properties of small amount of charge accumulation about 5 to 20 C/m3 and within short saturation time about 1.0 minutes. This paper summarizes the relationship between the properties of charge accumulation and chemical structural formula, and compares between the electro static potential distribution with negative charged polymer and its chemical structural formula.

  4. Effective Charge on Polymer Colloids Obtained Using a Renormalization Model.

    Science.gov (United States)

    Quesada-Pérez; Callejas-Fernández; Hidalgo-Álvarez

    1998-10-01

    Static light scattering has been used to study the electrostatic interaction between colloidal particles. Experiments were carried out using a latex with a very small diameter, allowing structure determination at high particle concentration. The obtained effective charge characterizing this interaction is found to be smaller than the bare charge determined from titration. A renormalization model connecting both values has been used. The agreement between the renormalized charge and that obtained from scattering data seems to point out that this model operates well. Copyright 1998 Academic Press.

  5. Piezo- and pyroelectricity of a polymer-foam space-charge electret

    Science.gov (United States)

    Neugschwandtner, Gerhard S.; Schwödiauer, Reinhard; Bauer-Gogonea, Simona; Bauer, Siegfried; Paajanen, Mika; Lekkala, Jukka

    2001-04-01

    Charged closed-cell polypropylene polymer foams are highly sensitive and broadband piezoelectric materials with a quasistatic piezoelectric d33 coefficient about 250 pC/N and a dynamic d33 coefficient of 140 pC/N at 600 kHz. The piezoelectric coefficient is much larger than that of ferroelectric polymers, like polyvinylidene fluoride, and compares favorably with ferroelectric ceramics, such as lead zirconate titanate. The pyroelectric coefficient p3=0.25 μC/m2 K is small in comparison to ferroelectric polymers and ferroelectric ceramics. The low density, small pyroelectric coefficient and high piezoelectric sensitivity make charged polymer foams attractive for a wide range of sensor and transducer applications in acoustics, air-borne ultrasound, medical diagnostics, and nondestructive testing.

  6. Spin-charge transformation of lattice fermion models: duality approach for diagrammatic simulation of strongly correlated systems

    Science.gov (United States)

    Carlström, Johan

    2017-09-01

    I derive a dual description of lattice fermions, specifically focusing on the t-J and Hubbard models, that allow diagrammatic techniques to be employed efficiently in the strongly correlated regime, as well as for systems with a restricted Hilbert space. These constructions are based on spin-charge transformation, where the lattice fermions of the original model are mapped onto spins and spin-less fermions. This mapping can then be combined with Popov-Fedotov fermionisation, where the spins are mapped onto lattice fermions with imaginary chemical potential. The resulting models do not contain any large expansion parameters, even for strongly correlated systems. Also, they exhibit dramatically smaller corrections to the density matrix from nonlinear terms in the Hamiltonian. The combination of these two properties means that they can be addressed with diagrammatic methods, including simulation techniques based on stochastic sampling of diagrammatic expansions.

  7. Removal of charged micropollutants from water by ion-exchange polymers -- effects of competing electrolytes.

    Science.gov (United States)

    Bäuerlein, Patrick S; Ter Laak, Thomas L; Hofman-Caris, Roberta C H M; de Voogt, Pim; Droge, Steven T J

    2012-10-15

    A wide variety of environmental compounds of concern, e.g. pharmaceuticals or illicit drugs, are acids or bases that may predominantly be present as charged species in drinking water sources. These charged micropollutants may prove difficult to remove by currently used water treatment steps (e.g. UV/H(2)O(2), activated carbon (AC) or membranes). We studied the sorption affinity of some ionic organic compounds to both AC and different charged polymeric materials. Ion-exchange polymers may be effective as additional extraction phases in water treatment, because sorption of all charged compounds to oppositely charged polymers was stronger than to AC, especially for the double-charged cation metformin. Tested below 1% of the polymer ion-exchange capacity, the sorption affinity of charged micropollutants is nonlinear and depends on the composition of the aqueous medium. Whereas oppositely charged electrolytes do not impact sorption of organic ions, equally charged electrolytes do influence sorption indicating ion-exchange (IE) to be the main sorption mechanism. For the tested polymers, a tenfold increased salt concentration lowered the IE-sorption affinity by a factor two. Different electrolytes affect IE with organic ions in a similar way as inorganic ions on IE-resins, and no clear differences in this trend were observed between the sulphonated and the carboxylated cation-exchanger. Sorption of organic cations is five fold less in Ca(2+) solutions compared to similar concentrations of Na(+), while that of anionic compounds is three fold weaker in SO(4)(2-) solutions compared to equal concentrations of Cl(-).

  8. Effect of deposition charges on the wettability performance of electrochromic polymers

    Science.gov (United States)

    Çağlar, Aysel; Cengiz, Uğur; Yıldırım, Mehmet; Kaya, İsmet

    2015-03-01

    Electrochromic polymers have been designed as future candidates for electrochromic displays (ECDs) and smart windows. This class of conducting polymers has been studied with their several optical properties as well as spectroelectrochemical stabilities. In practical use their contamination and abrasion could be expected to be main problem as exposed to moisture and other possible pollutants. In this study, we present a perspective to well-known electrochromic polymers in the words of their durable use. For this aim, a series of electrochromic polymers are deposited on indium tin oxide (ITO) coated glass plates by bulk electrolysis. Polymeric films are deposited by varied deposition charges (Qs) ranging from 62 to 620 mC cm-2 for comparison. Equilibrium water contact angle (θwaterequ) measurements of the prepared surfaces are measured by Attention Theta Optical Tensiometer. Surface roughness parameters (RMS) are determined by atomic force microscopy (AFM) technique and used for interpretation of hydrophobic-hydrophilic characteristics. The results clearly indicate that; poly(ethylenedioxythiophene) (PEDOT) has a hydrophilic surface whose hydrophilicity is increased by applied deposition charge and becomes a superhydrophile at high deposition charges. Among the tested polymers polycarbazole (PCarb) is the most promising long lifetime candidate due to its relatively hydrophobic character. Also, the hydrophobicity of PCarb is linearly increased by increasing deposition charge and reaches an optimum point at a particular condition.

  9. Statistical geometry of lattice chain polymers with voids of defined shapes: Sampling with strong constraints

    Science.gov (United States)

    Lin, Ming; Chen, Rong; Liang, Jie

    2008-02-01

    Proteins contain many voids, which are unfilled spaces enclosed in the interior. A few of them have shapes compatible to ligands and substrates and are important for protein functions. An important general question is how the need for maintaining functional voids is influenced by, and affects other aspects of proteins structures and properties (e.g., protein folding stability, kinetic accessibility, and evolution selection pressure). In this paper, we examine in detail the effects of maintaining voids of different shapes and sizes using two-dimensional lattice models. We study the propensity for conformations to form a void of specific shape, which is related to the entropic cost of void maintenance. We also study the location that voids of a specific shape and size tend to form, and the influence of compactness on the formation of such voids. As enumeration is infeasible for long chain polymer, a key development in this work is the design of a novel sequential Monte Carlo strategy for generating large number of sample conformations under very constraining restrictions. Our method is validated by comparing results obtained from sampling and from enumeration for short polymer chains. We succeeded in accurate estimation of entropic cost of void maintenance, with and without an increasing number of restrictive conditions, such as loops forming the wall of void with fixed length, with additionally fixed starting position in the sequence. Additionally, we have identified the key structural properties of voids that are important in determining the entropic cost of void formation. We have further developed a parametric model to predict quantitatively void entropy. Our model is highly effective, and these results indicate that voids representing functional sites can be used as an improved model for studying the evolution of protein functions and how protein function relates to protein stability.

  10. Analysis of charge photogeneration as a key determinant of photocurrent density in polymer: fullerene solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Tracey M.; Shoaee, Safa; Soon, Ying W.; Durrant, James R. [Centre for Plastic Electronics, Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Ballantyne, Amy; Nelson, Jenny [Centre for Plastic Electronics, Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Duffy, Warren; Heeney, Martin; McCulloch, Iain [Centre for Plastic Electronics, Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Merck Chemicals, Chilworth Science Park, Southampton SO16 7QD (United Kingdom)

    2010-12-07

    Charge photogeneration: The correlation between the efficiency of photogeneration of dissociated polarons and photocurrent densities for organic solar cells based on polymer:fullerene blend films is investigated. Optical assays of polaron yield measured in films without electrodes show a remarkably clear correlation with short circuit density and quantum yield measured in complete devices. For the blend films studied herein, the primary determinant of photocurrent generation is the efficiency of dissociation of photogenerated charges away from the polymer/fullerene interface and the primary loss pathway is geminate recombination. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Charged Polymer-Coated Separators by Atmospheric Plasma-Induced Grafting for Lithium-Ion Batteries.

    Science.gov (United States)

    Han, Mina; Kim, Dong-Won; Kim, Yeong-Cheol

    2016-10-05

    A simple and fast method of atmospheric plasma-induced grafting was applied over a polyethylene membrane to enhance its performance as a separator for lithium-ion batteries. The process of grafting has formed a thin, durable, and uniform layer on the surface of the porous membrane. The charges of grafted polymers affected the performance of batteries in many ways besides the change of hydrophilicity. Negative charges in polymers improve the capacity retention of batteries and the uniformity of the SEI layer. On the other hand, the electrostatic attraction between different charges contributed to small increases of thermal stability and mechanical strength of separators. Polyampholyte was grafted by using the mixtures of monomers, and the composition of the grafted layer was optimized. The formation of stable uniform SEI layers and the marked improvement in capacity retention were observed in the full cell tests of the lithium battery with the polyampholyte-grafted separators when the polyampholyte has a negative net charge.

  12. Generalized Courant-Snyder theory for coupled transverse dynamics of charged particles in electromagnetic focusing lattices

    Directory of Open Access Journals (Sweden)

    Hong Qin

    2009-06-01

    Full Text Available The Courant-Snyder theory gives a complete description of the uncoupled transverse dynamics of charged particles in electromagnetic focusing lattices. In this paper, the Courant-Snyder theory is generalized to the case of coupled transverse dynamics with two degrees of freedom. The generalized theory has the same structure as the original Courant-Snyder theory for one degree of freedom. The four basic components of the original Courant-Snyder theory, i.e., the envelope equation, phase advance, transfer matrix, and the Courant-Snyder invariant, all have their counterparts, with remarkably similar expressions, in the generalized theory presented here. In the generalized theory, the envelope function is generalized into an envelope matrix, and the envelope equation becomes a matrix envelope equation with matrix operations that are noncommutative. The generalized theory gives a new parametrization of the 4D symplectic transfer matrix that has the same structure as the parametrization of the 2D symplectic transfer matrix in the original Courant-Snyder theory. All of the parameters used in the generalized Courant-Snyder theory correspond to physical quantities of importance, and this parametrization can provide a valuable framework for accelerator design and particle simulation studies. A time-dependent canonical transformation is used to develop the generalized Courant-Snyder theory. Applications of the new theory to strongly and weakly coupled dynamics are given. It is shown that the stability of coupled dynamics can be determined by the generalized phase advance developed. Two stability criteria are given, which recover the known results about sum and difference resonances in the weakly coupled limit.

  13. Photoconductivity and Charge-Carrier Photogeneration in Photorefractive Polymers

    NARCIS (Netherlands)

    Däubler, Thomas K.; Kulikovsky, Lazar; Neher, Dieter; Cimrová, Vera; Hummelen, J.C.; Mecher, Erwin; Bittner, Reinhard; Meerholz, Klaus; Lawson, M.; Meerholz, Klaus

    2002-01-01

    We have studied photogeneration, transport, trapping and recombination as the governing mechanisms for the saturation field strength and the time response of the photorefractive (PR) effect in PVK-based PR materials, utilizing xerographic discharge and photoconductivity experiments. Both the charge

  14. Photoconductivity and Charge-Carrier Photogeneration in Photorefractive Polymers

    NARCIS (Netherlands)

    Däubler, Thomas K.; Kulikovsky, Lazar; Neher, Dieter; Cimrová, Vera; Hummelen, J.C.; Mecher, Erwin; Bittner, Reinhard; Meerholz, Klaus; Lawson, M.; Meerholz, Klaus

    2002-01-01

    We have studied photogeneration, transport, trapping and recombination as the governing mechanisms for the saturation field strength and the time response of the photorefractive (PR) effect in PVK-based PR materials, utilizing xerographic discharge and photoconductivity experiments. Both the charge

  15. Charge-driven and reversible assembly of ultra-dense polymer brushers: Formation and antifouling properties of a zipper brush

    NARCIS (Netherlands)

    Vos, de W.M.; Meijer, G.; Keizer, de A.; Cohen Stuart, M.A.; Kleijn, J.M.

    2010-01-01

    We investigated a new type of polymer brushes: the zipper brush. By adsorbing a diblock-copolymer with one charged block and one neutral block to an oppositely charged polyelectrolyte brush, a neutral polymer brush is formed on top of an almost neutral complex layer of polyelectrolytes. This neutral

  16. Yielding and flow of cellulose microfibril dispersions in the presence of a charged polymer

    NARCIS (Netherlands)

    Kort, De Daan W.; Veen, Sandra J.; As, Van Henk; Bonn, Daniel; Velikov, Krassimir P.; Duynhoven, Van John P.M.

    2016-01-01

    The shear flow of microfibrillated cellulose dispersions is still not wholly understood as a consequence of their multi-length-scale heterogeneity. We added carboxymethyl cellulose, a charged polymer, that makes cellulose microfibril dispersions more homogeneous at the submicron and macro scales.

  17. Enhancement of charge-transport characteristics in polymeric films using polymer brushes

    DEFF Research Database (Denmark)

    Whiting, G.L.; Snaith, H.J.; Khodabakhsh, S.

    2006-01-01

    We show that charge-transporting polymer chains in the brush conformation can be synthesized from a variety of substrates of interest, displaying a high degree of stretching and showing up to a 3 orders of magnitude increase in current density normal to the substrate as compared with a spin-coated...

  18. Charge carrier recombination dynamics in perovskite and polymer solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Paulke, Andreas; Kniepert, Juliane; Kurpiers, Jona; Wolff, Christian M.; Schön, Natalie; Brenner, Thomas J. K.; Neher, Dieter [Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24–25, 14476, Potsdam (Germany); Stranks, Samuel D. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Snaith, Henry J. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom)

    2016-03-14

    Time-delayed collection field experiments are applied to planar organometal halide perovskite (CH{sub 3}NH{sub 3}PbI{sub 3}) based solar cells to investigate charge carrier recombination in a fully working solar cell at the nanosecond to microsecond time scale. Recombination of mobile (extractable) charges is shown to follow second-order recombination dynamics for all fluences and time scales tested. Most importantly, the bimolecular recombination coefficient is found to be time-dependent, with an initial value of ca. 10{sup −9} cm{sup 3}/s and a progressive reduction within the first tens of nanoseconds. Comparison to the prototypical organic bulk heterojunction device PTB7:PC{sub 71}BM yields important differences with regard to the mechanism and time scale of free carrier recombination.

  19. Application of graph theory to the statistical thermodynamics of lattice polymers. I. Elements of theory and test for dimers

    Science.gov (United States)

    Brazhnik, Olga D.; Freed, Karl F.

    1996-07-01

    The lattice cluster theory (LCT) is extended to enable inclusion of longer range correlation contributions to the partition function of lattice model polymers in the athermal limit. A diagrammatic technique represents the expansion of the partition function in powers of the inverse lattice coordination number. Graph theory is applied to sort, classify, and evaluate the numerous diagrams appearing in higher orders. New general theorems are proven that provide a significant reduction in the computational labor required to evaluate the contributions from higher order correlations. The new algorithm efficiently generates the correction to the Flory mean field approximation from as many as eight sterically interacting bonds. While the new results contain the essential ingredients for treating a system of flexible chains with arbitrary lengths and concentrations, the complexity of our new algorithm motivates us to test the theory here for the simplest case of a system of lattice dimers by comparison to the dimer packing entropies from the work of Gaunt. This comparison demonstrates that the eight bond LCT is exact through order φ5 for dimers in one through three dimensions, where φ is the volume fraction of dimers. A subsequent work will use the contracted diagrams, derived and tested here, to treat the packing entropy for a system of flexible N-mers at a volume fraction of φ on hypercubic lattices.

  20. High yield sample preconcentration using a highly ion-conductive charge-selective polymer.

    Science.gov (United States)

    Chun, Honggu; Chung, Taek Dong; Ramsey, J Michael

    2010-07-15

    The development and analysis of a microfluidic sample preconcentration system using a highly ion-conductive charge-selective polymer [poly-AMPS (2-acrylamido-2-methyl-1-propanesulfonic acid)] is reported. The preconcentration is based on the phenomenon of concentration polarization which develops at the boundaries of the poly-AMPS with buffer solutions. A negatively charged polymer, poly-AMPS, positioned between two microchannels efficiently extracts cations through its large cross section, resulting in efficient anion sample preconcentration. The present work includes the development of a robust polymer that is stable over a wide range of buffers with varying chemical compositions. The sample preconcentration effect remains linear to over 3 mM (0.15 pmol) and 500 microM (15 fmol) for fluorescein and TRITC-tagged albumin solutions, respectively. The system can potentially be used for concentrating proteins on microfluidic devices with subsequent analysis for proteomic applications.

  1. Influence of nanoparticle shape on charge transport and recombination in polymer/nanocrystal solar cells.

    Science.gov (United States)

    Li, Zhe; Wang, Weiyuan; Greenham, Neil C; McNeill, Christopher R

    2014-12-21

    A key consideration for the efficient operation of hybrid solar cells based upon conjugated polymers and inorganic semiconductor nanocrystals is charge transport in the nanocrystal phase. Here we report the results of a study into the charge transport kinetics of polymer/nanocrystal solar cells based on blends poly(3-hexylthiophene) (P3HT) with either CdSe nano-dots or CdSe nano-tetrapods. Transient photocurrent measurements reveal significant differences in the charge transport kinetics of nano-dot and nano-tetrapod hybrid cells, with the charge collection of the P3HT/CdSe nano-dot device severely limited by charge trapping. In comparison the nano-tetrapod cell exhibits significantly reduced charge trapping compared to the nano-dot cell accounting for the improved fill-factor and overall device efficiency. Transient photovoltage measurements have also been employed that demonstrate slower recombination rates in the P3HT/CdSe tetrapod device compared to the P3HT/CdSe dot device. These observations directly identify nanoparticle shape as a critical factor influencing the charge transport and hence recombination in this benchmark hybrid system, confirming the hypothesis that the use of tetrapods improves device performance through an improvement in electron transport in the nanocrystal phase.

  2. Intersections of thick Center Vortices, Dirac Eigenmodes and Fractional Topological Charge in SU(2) Lattice Gauge Theory

    CERN Document Server

    Höllwieser, Roman; Heller, Urs M

    2011-01-01

    Intersections of thick, plane vortices are characterized by the topological charge $|Q|=1/2$. We compare such intersections with the distribution of zeromodes of the Dirac operator in the fundamental and adjoint representation using both the overlap and asqtad staggered fermion formulations in SU(2)-lattice gauge theory. We analyze configurations with four intersections and find that the probability density distribution of fundamental zeromodes in the intersection plane differs significantly from the one obtained analytically in [Phys.\\ Rev.\\ D 66, 85004 (2002)]. The Dirac eigenmodes are clearly sensitive to the traces of the Polyakov (Wilson) lines and do not exactly locate topological charge contributions. Although, the adjoint Dirac operator is able to produce zeromodes for configurations with topological charge $|Q|=1/2$, they do not locate single vortex intersections, as we prove by forming arbitrary linear combinations of these zeromodes - their scalar density peaks at least at two intersection points. ...

  3. Charge-patterning phase transition on a surface lattice of titratable sites adjacent to an electrolyte solution

    Science.gov (United States)

    Shore, Joel; Thurston, George

    We discuss a model for a charge-patterning phase transition on a two-dimensional square lattice of titratable sites, here regarded as protonation sites, placed on a square lattice in a dielectric medium just below the planar interface between this medium and an aqueous salt solution. Within Debye-Huckel theory, the analytical form of the electrostatic repulsion between protonated sites exhibits an approximate inverse cubic power-law decrease beyond short distances. The problem can thus be mapped onto the two-dimensional antiferromagnetic Ising model with this longer-range interaction, which we study with Monte Carlo simulations. As we increase pH, the occupation probability of a site decreases from 1 at low pH to 0 at high pH. For sufficiently-strong interaction strengths, a phase transition occurs as the occupation probability of 1/2 is approached: the charges arrange themselves into a checkerboard pattern. This ordered phase persists over a range of pH until a transition occurs back to a disordered state. This state is the analogue of the Neel state in the antiferromagnetic Ising spin model. More complicated ordered phases are expected for sufficiently strong interactions (with occupation probabilities of 1/4 and 3/4) and if the lattice is triangular rather than square. This work was supported by NIH EY018249 (GMT).

  4. Probing spin-charge relation by magnetoconductance in one-dimensional polymer nanofibers

    Science.gov (United States)

    Park, Yung Woo

    2013-03-01

    Polymer nanofibers are one dimensional (1-D) organic hydrocarbon systems containing conducting polymers where the non-linear local excitations such as solitons, polarons and bipolarons formed by the electron-phonon interaction were predicted. Magnetoconductance (MC) can simultaneously probe both the spin and charge of these mobile species and identify the effects of electron-electron interactions on these nonlinear excitations. Here we report our observations of a qualitatively different MC in polyacetylene (PA) and in polyaniline (PANI) and polythiophene (PT) nanofibers. In PA the MC is essentially zero, but it is present in PANI and PT. The universal scaling behavior and the zero (finite) MC in PA (PANI and PT) nanofibers provide evidence of Coulomb interactions between spinless charged solitons (interacting polarons which carry both spin and charge).

  5. Unraveling the Electronic Heterogeneity of Charge Traps in Conjugated Polymers by Single-Molecule Spectroscopy.

    Science.gov (United States)

    Adachi, Takuji; Vogelsang, Jan; Lupton, John M

    2014-02-06

    Charge trapping is taken for granted in modeling the characteristics of organic semiconductor devices, but very few techniques actually exist to spectroscopically pinpoint trap states. For example, trap levels are often assumed to be discrete in energy. Using the well-known keto defect in polyfluorene as a model, we demonstrate how single-molecule spectroscopy can directly track the formation of charge and exciton traps in conjugated polymers in real time, providing crucial information on the energetic distribution of trap sites relative to the polymer optical gap. Charge traps with universal spectral fingerprints scatter by almost 1 eV in depth, implying that substantial heterogeneity must be taken into account when modeling devices.

  6. Impact of charge carrier injection on single-chain photophysics of conjugated polymers

    CERN Document Server

    Hofmann, Felix J; Lupton, John M

    2016-01-01

    Charges in conjugated polymer materials have a strong impact on the photophysics and their interaction with the primary excited state species has to be taken into account in understanding device properties. Here, we employ single-molecule spectroscopy to unravel the influence of charges on several photoluminescence (PL) observables. The charges are injected either stochastically by a photochemical process, or deterministically in a hole-injection sandwich device configuration. We find that upon charge injection, besides a blue-shift of the PL emission and a shortening of the PL lifetime due to quenching and blocking of the lowest-energy chromophores, the non-classical photon arrival time distribution of the multichromophoric chain is modified towards a more classical distribution. Surprisingly, the fidelity of photon antibunching deteriorates upon charging, whereas one would actually expect the number of chromophores to be reduced. A qualitative model is presented to explain the observed PL changes. The resul...

  7. Charge transport in photochemically modified molecularly doped polymers

    Science.gov (United States)

    Stasiak, James W.; Storch, Teresa J.; Mao, Erji

    1995-08-01

    Hole mobilities in p-diethylaminobenzaldehyde diphenylhydrazone (DEH) doped polycarbonate films are determined using the time-of-flight transient photocurrent technique. Measurements of hole transport parameters are determined over a range of electric fields before and after the samples are deliberately irradiated with UV light. UV irradiation of the hole transport molecule DEH results in the creation of a photoproduct, 1-phenyl-3-(4- diethylamino-1-phenyl)-1, 3-indazole with moderately high efficiency. Once formed, this photoproduct has been shown to act as a barrier to hole conduction. We exploit this photochemical reaction to examine the hole transport properties in a molecularly doped polymer system containing DEH doped polycarbonate. We propose that the increase in concentration of the photoproduct modifies the intrinsic order of the system and provides a unique probe to distinguish between the disorder formalism of Baessler and coworkers and models which propose polaron formation.

  8. MODELLING OF CHARGE CARRIER MOBILITY FOR TRANSPORT BETWEEN ELASTIC POLYACETYLENE-LIKE POLYMER NANORODS

    Directory of Open Access Journals (Sweden)

    M. Mensik

    2017-03-01

    Full Text Available A quantum model solving the charge carrier mobility between polyacetylene-like polymer nanorods is presented. The model assumes: a Quantum mechanical calculation of hole on-chain delocalization involving electron-phonon coupling leading to the Peierls instability, b Hybridization coupling between the polymer backbone and side-groups (or environmental states, which act as hole traps, and c Semiclassical description of the inter-chain hole transfer in an applied voltage based on Marcus theory. We have found that mobility resonantly depends on the hybridization coupling between polymer and linked groups. We observed also non-trivial mobility dependences on the difference of energies of the highest occupied molecular orbitals localized on the polymer backbone and side-groups, respectively, and hole concentration. Those findings are important for optimization of hybrid opto-electronic devices.

  9. Charge Transfer Channels in Formation of Exciplex in Polymer Blends

    Institute of Scientific and Technical Information of China (English)

    DOU Fei; ZHANG Xin-Ping

    2011-01-01

    The strong dependence of photoluminescence of charge transfer excited states or exciplex in a blend film of poly(9,9'-dioctylBuorene-co-benzothiadiazole) (F8BT) and poly(9,9'-dioctyl6uorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-l,4- phenylenediamine) (PFB) on the excitation wavelengths and morphology is investigated. The experimental results reveal that electron transfer in the LUMOs from PFB to F8BT is more efficient than hole transfer in the HOMOs from PFB to F8BT for the formation of exciplex at the interfacial junctions between these two types of molecules in the blend Sim. Furthermore, energy transfer from the blue-emitting PFB to the green-emitting F8BT at the interfaces introduces an additional two-step channel and thus enhances the formation of an exciplex. This is important for understanding of charge generation and separation in organic bulk heterojunctions and for design of optoelectronic devices.%@@ The strong dependence of photoluminescence of charge transfer excited states or exciplex in a blend film of poly(9,9'-dioctylfluorene-co-benzothiadiazole)(F8BT)and poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine)(PFB)on the excitation wavelengths and morphology is investigated.The experimental results reveal that electron transfer in the LUMOs from PFB to F8BT is more efficient than hole transfer in the HOMOs from PFB to F8BT for the formation of exciplex at the interfacial junctions between these two types of molecules in the blend film.Furthermore,energy transfer from the blue-emitting PFB to the green-emitting F8BT at the interfaces introduces an additional two-step channel and thus enhances the formation of an exciplex.This is important for understanding of charge generation and separation in organic bulk heterojunctions and for design of optoelectronic devices.

  10. Recent progress of the characterization of oppositely charged polymer/surfactant complex in dilution deposition system.

    Science.gov (United States)

    Miyake, M

    2017-01-01

    A mixture of oppositely charged polymer and surfactants changes the solubilized state, having a complex precipitation region at the composition of electric neutralization. This complex behavior has been applied to surface modification in the fields of health care and cosmetic products such as conditioning shampoos, as a dilution-deposition system in which the polymer/surfactant mixture at the higher surfactant concentration precipitates the insoluble complex by dilution. A large number of studies over many years have revealed the basic coacervation behavior and physicochemical properties of complexes. However, the mechanism by which a precipitated complex performs surface modification is not well understood. The precipitation region and the morphology of precipitated complex that are changed by molecular structure and additives affect the performance. Hydrophilic groups such as the EO unit in polymers and surfactants, the mixing of nonionic or amphoteric surfactant and nonionic polymer, and the addition of low polar solvent influence the complex precipitation region. Furthermore, the morphology of precipitated complex is formed by crosslinking and aggregating among polymers in the dilution process, and characterizes the performance of products. The polymer chain density in precipitated complex is determined by the charges of both the polymer and surfactant micelle and the conformation of polymer. As a result, the morphology of precipitated complexes is changed from a closely packed film to looser meshes, and/or to small particles, and it is possible for the morphology to control the rheological properties and the amount of adsorbed silicone. In the future, further investigation of the relationships between the morphology and performance is needed.

  11. Charge carrier mobility in conjugated organic polymers: simulation of an electron mobility in a carbazole-benzothiadiazole-based polymer

    Science.gov (United States)

    Li, Yaping; Lagowski, Jolanta B.

    2011-08-01

    Inorganic (mostly silicon based) solar cells are important devices that are used to solve the world energy and environmental needs. Now days, organic solar cells are attracting considerable attention in the field of photovoltaic cells because of their low cost and processing flexibility. Often conjugated polymers are used in the construction of the organic solar cells. We study the conjugated polymers' charge transport using computational approach that involves the use of the density functional theory (DFT), semiempirical (ZINDO), and Monte Carlo (MC) theoretical methods in order to determine their transfer integrals, reorganization energies, transfer rates (with the use of Marcus-Hush equation) and mobilities. We employ the experimentally determined three dimensional (3D) structure of poly(9,9'-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) to estimate the electron mobility in a similar co-alternating polymer consisting of carbazole and benzothiadiazole units (C8BT). In agreement with our previous work, we found that including an orientational disorder in the crystal reduces the electron mobility in C8BT. We hope that the proposed computational approach can be used to predict charge mobility in organic materials that are used in solar cells.

  12. Confronting fluctuations of conserved charges in central nuclear collisions at the LHC with predictions from Lattice QCD

    Science.gov (United States)

    Braun-Munzinger, P.; Kalweit, A.; Redlich, K.; Stachel, J.

    2016-12-01

    We construct net baryon number and strangeness susceptibilities as well as correlations between electric charge, strangeness and baryon number from experimental data on the particle production yields at midrapidity of the ALICE Collaboration at CERN. The data were taken in central Pb-Pb collisions at √{sNN} = 2.76 TeV and cover one unit of rapidity. We show that the resulting fluctuations and correlations are consistent with Lattice QCD results at the chiral crossover pseudocritical temperature Tc ≃ 155 MeV. This agreement lends strong support to the assumption that the fireball created in these collisions is of thermal origin and exhibits characteristic properties expected in QCD at the transition from the quark gluon plasma to the hadronic phase. Since Lattice QCD calculations are performed at a baryochemical potential of μB = 0, the comparisons with LHC data are the most direct due to the vanishing baryon transport to midrapidity at these high energies.

  13. Enhancing pseudocapacitive charge storage in polymer templated mesoporous materials.

    Science.gov (United States)

    Rauda, Iris E; Augustyn, Veronica; Dunn, Bruce; Tolbert, Sarah H

    2013-05-21

    Growing global energy demands coupled with environmental concerns have increased the need for renewable energy sources. For intermittent renewable sources like solar and wind to become available on demand will require the use of energy storage devices. Batteries and supercapacitors, also known as electrochemical capacitors (ECs), represent the most widely used energy storage devices. Supercapacitors are frequently overlooked as an energy storage technology, however, despite the fact that these devices provide greater power, much faster response times, and longer cycle life than batteries. Their limitation is that the energy density of ECs is significantly lower than that of batteries, and this has limited their potential applications. This Account reviews our recent work on improving pseudocapacitive energy storage performance by tailoring the electrode architecture. We report our studies of mesoporous transition metal oxide architectures that store charge through surface or near-surface redox reactions, a phenomenon termed pseudocapacitance. The faradaic nature of pseudocapacitance leads to significant increases in energy density and thus represents an exciting future direction for ECs. We show that both the choice of material and electrode architecture is important for producing the ideal pseudocapacitor device. Here we first briefly review the current state of electrode architectures for pseudocapacitors, from slurry electrodes to carbon/metal oxide composites. We then describe the synthesis of mesoporous films made with amphiphilic diblock copolymer templating agents, specifically those optimized for pseudocapacitive charge storage. These include films synthesized from nanoparticle building blocks and films made from traditional battery materials. In the case of more traditional battery materials, we focus on using flexible architectures to minimize the strain associated with lithium intercalation, that is, the accumulation of lithium ions or atoms between the

  14. Enhancing charge storage of conjugated polymer electrodes with phenolic acids

    Science.gov (United States)

    Wagner, Michal; Rębiś, Tomasz; Inganäs, Olle

    2016-01-01

    We here present studies of electrochemical doping of poly(1-aminoanthraquinone) (PAAQ) films with three structurally different phenolic acids. The examined phenolic acids (sinapic, ferulic and syringic acid) were selected due to their resemblance to redox active groups, which can be found in lignin. The outstanding electrochemical stability of PAAQ films synthesized for this work enabled extensive cycling of phenolic acid-doped PAAQ films. Potentiodynamic and charge-discharge studies revealed that phenolic acid-doped PAAQ films exhibited enhanced capacitance in comparison to undoped PAAQ films, together with appearance of redox activity characteristics specific for each dopant. Electrochemical kinetic studies performed on microelectrodes affirmed the fast electron transfer for hydroquinone-to-quinone reactions with these phenolic compounds. These results imply the potential application of phenolic acids in cheap and degradable energy storage devices.

  15. Roughening Conjugated Polymer Surface for Enhancing the Charge Collection Efficiency of Sequentially Deposited Polymer/Fullerene Photovoltaics

    Directory of Open Access Journals (Sweden)

    Yoonhee Jang

    2015-08-01

    Full Text Available A method that enables the formation of a rough nano-scale surface for conjugated polymers is developed through the utilization of a polymer chain ordering agent (OA. 1-Chloronaphthalene (1-CN is used as the OA for the poly(3-hexylthiophene-2,5-diyl (P3HT layer. The addition of 1-CN to the P3HT solution improves the chain ordering of the P3HT during the film formation process and increases the surface roughness of the P3HT film compared to the film prepared without 1-CN. The roughened surface of the P3HT film is utilized to construct a P3HT/fullerene bilayer organic photovoltaic (OPV by sequential solution deposition (SqSD without thermal annealing process. The power conversion efficiency (PCE of the SqSD-processed OPV utilizing roughened P3HT layer is 25% higher than that utilizing a plain P3HT layer. It is revealed that the roughened surface of the P3HT increases the heterojunction area at the P3HT/fullerene interface and this resulted in improved internal charge collection efficiency, as well as light absorption efficiency. This method proposes a novel way to improve the PCE of the SqSD-processed OPV, which can be applied for OPV utilizing low band gap polymers. In addition, this method allows for the reassessment of polymers, which have shown insufficient performance in the BSD process.

  16. 2D coherent charge transport in highly ordered conducting polymers doped by solid state diffusion

    Science.gov (United States)

    Kang, Keehoon; Watanabe, Shun; Broch, Katharina; Sepe, Alessandro; Brown, Adam; Nasrallah, Iyad; Nikolka, Mark; Fei, Zhuping; Heeney, Martin; Matsumoto, Daisuke; Marumoto, Kazuhiro; Tanaka, Hisaaki; Kuroda, Shin-Ichi; Sirringhaus, Henning

    2016-08-01

    Doping is one of the most important methods to control charge carrier concentration in semiconductors. Ideally, the introduction of dopants should not perturb the ordered microstructure of the semiconducting host. In some systems, such as modulation-doped inorganic semiconductors or molecular charge transfer crystals, this can be achieved by spatially separating the dopants from the charge transport pathways. However, in conducting polymers, dopants tend to be randomly distributed within the conjugated polymer, and as a result the transport properties are strongly affected by the resulting structural and electronic disorder. Here, we show that in the highly ordered lamellar microstructure of a regioregular thiophene-based conjugated polymer, a small-molecule p-type dopant can be incorporated by solid state diffusion into the layers of solubilizing side chains without disrupting the conjugated layers. In contrast to more disordered systems, this allows us to observe coherent, free-electron-like charge transport properties, including a nearly ideal Hall effect in a wide temperature range, a positive magnetoconductance due to weak localization and the Pauli paramagnetic spin susceptibility.

  17. Photoelectrochemical reaction in conducting polymers for solar energy harvesting and charge storage

    Science.gov (United States)

    Rahimi, Fatemeh; Tevi, Tete; Takshi, Arash

    2016-09-01

    Energy storage is an essential ground for solar energy systems, particularly for the off-grid applications. Concurrent energy harvesting and charge storage in a photoactive supercapacitor has already been demonstrated. The key element in such a device is a conducting polymer which stores the charge via change in its redox states. In this work, we have studied the photoelectrochemical reactions in composites of polyaniline (PANI). We used the electrochemical deposition method for the polymer growth. The results of the current study indicate that the photo-reactivity of the materials largely depends on the electrolyte and the type of the dye molecule. Among different synthetic dyes, methylene blue has shown the strongest photoelectrochemical reaction in an HCl electrolyte. The cyclic voltammetry (CV) results showed that the amplitude of the redox peaks changes significantly upon illumination. The amount of stored charges in the polymer was estimated from the CV results. The results encourage the application of PANI for charge storage in a photoactive supercapacitor.

  18. Resonance analysis for a space charge dominated beam in a circular lattice

    Directory of Open Access Journals (Sweden)

    Marco Venturini

    2000-03-01

    Full Text Available We use the linearized Vlasov-Poisson equations to study the response of a Kapchinskij-Vladimirskij beam to magnetic multipole errors in a circular lattice. This work extends the calculation of Gluckstern [Proceedings of the Linac Conference, 1970 (Fermilab, Batavia, IL, 1970, p. 811] to the case of nonideal periodic lattices. The smooth approximation is assumed. We determine the resonance conditions as well as the amplitude of the excited collective modes as a function of the error size outside the stopbands. We find that the frequencies associated with lattice resonances are a subset of the beam natural eigenfrequencies. The result is used to study the motion of test particles crossing the boundary of the beam core. Close to resonance the model predicts the emergence of a halo if sufficiently large gradient errors are present. Application is made to the University of Maryland Electron Ring.

  19. From electrode charges on dielectric elastomers to trapped charges and electric dipoles in electrets and ferroelectrets: fundamental and applications-relevant aspects of diversity in electroactive polymers

    Science.gov (United States)

    Gerhard, Reimund

    2016-04-01

    Some recent developments in the areas of soft and basically incompressible electro-electrets (dielectric elastomers) with large strains, of anisotropic polymer ferro- or piezo-electrets with quasi-ferroelectric behavior, of moleculardipole electrets with significant ferro-, pyro- and piezo-electricity, and of space-charge polymer electrets with locally stabilised charges are described. Such materials may be applied, e.g., in soft actuators, energy harvesters and flexible and stretchable sensors for devices such as artificial muscles, electrically controllable refractive and diffractive optics, flexible pyroelectric detectors, motion and displacement sensors, earphones and microphones, ultrasonic transducers, air filters, radiation dosimeters, etc. The performance of dielectric elastomers for actuator, energy-harvester and sensor applications relies on a high relative permittivity and a low elastic modulus. High densities of electric charges in the electrodes are required in order to provide large Maxwell stresses or high energy densities. Significant amounts of localised or trapped charges, as well as electric dipoles from pairs of charges, lead to useful electro-mechanical and mechano-electrical effects (or inverse and direct piezoelectricity, respectively) if they are properly arranged in dielectric materials with extremely low conductivities. Space-charge electret films and ferroelectret systems should exhibit thermal and long-term stability of the trapped charges within the respective materials. Ferroelectric polymers and other polar polymers show useful piezo- and pyroelectric properties if their polymer-chain conformations allow for parallel packing of the molecular dipoles. Space-charge and molecular-dipole electrets are widely applied, e.g. in microphones, air filters, radiation dosimeters, ultrasonic transducers, etc. Basically, the performance of all electro-active polymers relies on the attraction (and repulsion) of electric charges and thus directly on

  20. Precision matched solution of the coupled beam envelope equations for a periodic quadrupole lattice with space charge

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Edward P.

    2002-02-01

    The coupled Kapchinskij-Vladimirskij (K-V) envelope equations for a charged particle beam transported by a periodic system of quadrupoles with self-consistent space charge force have previously been solved by various approximate methods, with accuracy ranging from 1% to 10%. A new method of solution is introduced here, which is based on a double expansion of the beam envelope functions in powers of the focal strength and either the beam's emittance or its dimensionless perveance. This method results in accuracy better than 0.1% for typical lattice and beam parameters when carried through one consistent level of approximation higher than employed in previous work. Several useful quantities, such as the values of the undepressed tune and the beam's perveance in the limit of vanishing emittance, are represented by very rapidly converging power series in the focal strength, with accuracy of .01% or better.

  1. Chiral Edge States and Fractional Charge Separation in a System of Interacting Bosons on a Kagome Lattice

    Science.gov (United States)

    Zhang, Xue-Feng; Eggert, Sebastian

    2013-10-01

    We consider the extended hard-core Bose-Hubbard model on a kagome lattice with boundary conditions on two edges. We find that the sharp edges lift the degeneracy and freeze the system into a striped order at 1/3 and 2/3 filling for zero hopping. At small hopping strengths, holes spontaneously appear and separate into fractional charges which move to the edges of the system. This leads to a novel edge liquid phase, which is characterized by fractional charges near the edges and a finite edge compressibility but no superfluid density. The compressibility is due to excitations on the edge which display a chiral symmetry breaking that is reminiscent of the quantum Hall effect and topological insulators. Large scale Monte Carlo simulations confirm the analytical considerations.

  2. Exact solution of the thermodynamics and size parameters of a polymer confined to a lattice of finite size: Large chain limit

    Energy Technology Data Exchange (ETDEWEB)

    Snyder, Chad R., E-mail: chad.snyder@nist.gov; Guttman, Charles M., E-mail: charles.guttman@nist.gov [Materials Science and Engineering Division, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899 (United States); Di Marzio, Edmund A., E-mail: edmund.dimarzio@nist.gov [Materials Science and Engineering Division, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899 (United States); Bio-Poly-Phase, 14205 Parkvale Road, Rockville, Maryland 20853 (United States)

    2014-01-21

    We extend the exact solutions of the Di Marzio-Rubin matrix method for the thermodynamic properties, including chain density, of a linear polymer molecule confined to walk on a lattice of finite size. Our extensions enable (a) the use of higher dimensions (explicit 2D and 3D lattices), (b) lattice boundaries of arbitrary shape, and (c) the flexibility to allow each monomer to have its own energy of attraction for each lattice site. In the case of the large chain limit, we demonstrate how periodic boundary conditions can also be employed to reduce computation time. Advantages to this method include easy definition of chemical and physical structure (or surface roughness) of the lattice and site-specific monomer-specific energetics, and straightforward relatively fast computations. We show the usefulness and ease of implementation of this extension by examining the effect of energy variation along the lattice walls of an infinite rectangular cylinder with the idea of studying the changes in properties caused by chemical inhomogeneities on the surface of the box. Herein, we look particularly at the polymer density profile as a function of temperature in the confined region for very long polymers. One particularly striking result is the shift in the critical condition for adsorption due to surface energy inhomogeneities and the length scale of the inhomogeneities; an observation that could have important implications for polymer chromatography. Our method should have applications to both copolymers and biopolymers of arbitrary molar mass.

  3. Two-dimensional charge transport in self-organized, high-mobility conjugated polymers

    DEFF Research Database (Denmark)

    Sirringhaus, H.; Brown, P.J.; Friend, R.H.

    1999-01-01

    Self-organization in many solution-processed, semiconducting conjugated polymers results in complex microstructures, in which ordered microcrystalline domains are embedded in an amorphous matrix(I). This has important consequences for electrical properties of these materials: charge transport...... is usually limited by the most difficult hopping processes and is therefore dominated by the disordered matrix, resulting in low charge-carrier mobilities(2) (less than or equal to 10(-5) cm(2)V(-1)s(-1)). Here we use thin-film, field-effect transistor structures to probe the transport properties...... of the ordered microcrystalline domains in the conjugated polymer poly(3-hexylthiophene), P3HT, Self-organization in P3HT results in a lamella structure with two-dimensional conjugated sheets formed by interchain stacking. We find that, depending on processing conditions, the lamellae can adopt two different...

  4. Porous cationic polymers: the impact of counteranions and charges on CO2 capture and conversion.

    Science.gov (United States)

    Buyukcakir, Onur; Je, Sang Hyun; Choi, Dong Shin; Talapaneni, Siddulu Naiudu; Seo, Yongbeom; Jung, Yousung; Polychronopoulou, Kyriaki; Coskun, Ali

    2016-01-18

    Porous cationic polymers (PCPs) with surface areas up to 755 m(2) g(-1) bearing positively charged viologen units in their backbones and different counteranions have been prepared. We have demonstrated that by simply varying counteranions both gas sorption and catalytic properties of PCPs can be tuned for metal-free capture and conversion of CO2 into value-added products such as cyclic carbonates with excellent yields.

  5. A Close Look at Charge Generation in Polymer:Fullerene Blends with Microstructure Control

    KAUST Repository

    Scarongella, Mariateresa

    2015-03-04

    © 2015 American Chemical Society. We reveal some of the key mechanisms during charge generation in polymer:fullerene blends exploiting our well-defined understanding of the microstructures obtained in pBTTT:PCBM systems via processing with fatty acid methyl ester additives. Based on ultrafast transient absorption, electro-absorption, and fluorescence up-conversion spectroscopy, we find that exciton diffusion through relatively phase-pure polymer or fullerene domains limits the rate of electron and hole transfer, while prompt charge separation occurs in regions where the polymer and fullerene are molecularly intermixed (such as the co-crystal phase where fullerenes intercalate between polymer chains in pBTTT:PCBM). We moreover confirm the importance of neat domains, which are essential to prevent geminate recombination of bound electron-hole pairs. Most interestingly, using an electro-absorption (Stark effect) signature, we directly visualize the migration of holes from intermixed to neat regions, which occurs on the subpicosecond time scale. This ultrafast transport is likely sustained by high local mobility (possibly along chains extending from the co-crystal phase to neat regions) and by an energy cascade driving the holes toward the neat domains.

  6. TITANIUM DIOXIDE TRIADS FOR IMPROVED CHARGE-SEPARATION USING CONDUCTIVE POLYMERS

    Energy Technology Data Exchange (ETDEWEB)

    Cochran, T.M.; Gaylor, T.N.; de la Garza, L.; Rajh, T.

    2009-01-01

    Dye-sensitized solar cells are potentially one of the best solutions to solar energy conversion because of the low cost of required materials and production processes. Titanium dioxide (TiO2) nanoparticulate fi lms are the basis for one of these types of cells, providing large surface area for dye-sensitizer adsorption. Because TiO2 nanoparticulate fi lms develop defects caused by oxygen defi ciency, deep reactive electron traps are formed. With the addition of an enediol ligand, these electron traps are deliberately removed, enhancing the conduction of electrons within the fi lm. In this project, TiO2 nanoparticulate fi lms made by a layer-by-layer dip coating method were modifi ed with 3,4-dihydroxyphenylacetic acid (DOPAC). DOPAC binds to the titanium atoms on the surface of the nanoparticles, restoring their octahedral geometry. This restructuring of the surface shifts the spectral properties of the TiO2 to the visible spectrum and improves the separation of charges which is observed using photoelectrochemistry. Furthermore, DOPAC enables the electronic attachment of other molecules to the surface of TiO2 fi lms, such as the conductive polymer polyaniline base. This conductive polymer provides an extended separation of charges which increases photocurrent production by forming a triad with the TiO2 semiconductor through the 3,4-dihydroxyphenylacetic acid linker. The photocurrent increases due to the donor properties of the conductive polymer thereby decreasing charge pair recombination.

  7. Molecular imprinted polymer with positively charged, assistant recognition polymer chains for adsorption/enrichment of low content target protein

    Institute of Scientific and Technical Information of China (English)

    LONG Yi; SUN Yang; WANG Ying; XING XiaoCui; ZHAO Zhuo; WANG ChunHong; FAN YunGe; MI HuaiFeng

    2008-01-01

    Here, we introduce a new type of molecular imprinted polymer (MIP) with immobilized assistant recog-nition polymer chains (ARPCs) to create effective recognition sites and with bacterial cloned protein as template for adsorbing the low content target protein from cell extract. In this work, cloned pig cyclo-philin 18 (pCyP18), a peptidyl-prolyl cis/trans-isomerase, was used as template. The template protein was selectively assembled with ARPCs from their library, which consists of numerous limited length polymer chains with randomly distributed recognition sites of positively charged amino groups and immobilizing sites. These assemblies were adsorbed by porous microsphers and immobilized on them.After removing the template, binding sites complementary to the target protein in size, shape and the position of recognition groups were exposed, and their confirmation was preserved by the cross-linked structure. The synthesized MIP was used to adsorb the cellular pCyP18, and its proportional content was enriched more than hundred times. The extended experiment on imprinting bovine serum albumin (BSA) with ARPCs shows that this method is also suitable for large protein.

  8. Analytical methods for describing charged particle dynamics in general focusing lattices using generalized Courant-Snyder theory

    Directory of Open Access Journals (Sweden)

    Hong Qin

    2014-04-01

    Full Text Available The dynamics of charged particles in general linear focusing lattices with quadrupole, skew-quadrupole, dipole, and solenoidal components, as well as torsion of the fiducial orbit and variation of beam energy is parametrized using a generalized Courant-Snyder (CS theory, which extends the original CS theory for one degree of freedom to higher dimensions. The envelope function is generalized into an envelope matrix, and the phase advance is generalized into a 4D symplectic rotation, or a U(2 element. The 1D envelope equation, also known as the Ermakov-Milne-Pinney equation in quantum mechanics, is generalized to an envelope matrix equation in higher dimensions. Other components of the original CS theory, such as the transfer matrix, Twiss functions, and CS invariant (also known as the Lewis invariant all have their counterparts, with remarkably similar expressions, in the generalized theory. The gauge group structure of the generalized theory is analyzed. By fixing the gauge freedom with a desired symmetry, the generalized CS parametrization assumes the form of the modified Iwasawa decomposition, whose importance in phase space optics and phase space quantum mechanics has been recently realized. This gauge fixing also symmetrizes the generalized envelope equation and expresses the theory using only the generalized Twiss function β. The generalized phase advance completely determines the spectral and structural stability properties of a general focusing lattice. For structural stability, the generalized CS theory enables application of the Krein-Moser theory to greatly simplify the stability analysis. The generalized CS theory provides an effective tool to study coupled dynamics and to discover more optimized lattice designs in the larger parameter space of general focusing lattices.

  9. The relationship between nanoscale architecture and charge transport in conjugated nanocrystals bridged by multichromophoric Polymers.

    Science.gov (United States)

    Dabirian, Reza; Palermo, Vincenzo; Liscio, Andrea; Schwartz, Erik; Otten, Matthijs B J; Finlayson, Chris E; Treossi, Emanuele; Friend, Richard H; Calestani, Gianluca; Müllen, Klaus; Nolte, Roeland J M; Rowan, Alan E; Samorì, Paolo

    2009-05-27

    We report on the self-assembly and the electrical characterization of bicomponent films consisting of an organic semiconducting small molecule blended with a rigid polymeric scaffold functionalized in the side chains with monomeric units of the same molecule. The molecule and polymer are a perylene-bis(dicarboximide) monomer (M-PDI) and a perylene-bis(dicarboximide)-functionalized poly(isocyanopeptide) (P-PDI), which have been codeposited on SiO(x) and mica substrates from solution. These bicomponent films have been characterized by atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM), revealing the relationship between architecture and function for various supramolecular nanocrystalline arrangements at a nanometer spatial resolution. Monomer-polymer interactions can be controlled by varying solvent and/or substrate polarity, so that either the monomer packing dictates the polymer morphology or vice versa, leading to a morphology exhibiting M-PDI nanocrystals connected with each other by P-PDI polymer wires. Compared to pure M-PDI or P-PDI films, those bicomponent films that possess polymer interconnections between crystallites of the monomer display a significant improvement in electrical connectivity and a 2 orders of magnitude increase in charge carrier mobility within the film, as measured in thin film transistor (TFT) devices. Of a more fundamental interest, our technique allows the bridging of semiconducting crystals, without the formation of injection barriers at the connection points.

  10. Effects of Confinement on Microstructure and Charge Transport in High Performance Semicrystalline Polymer Semiconductors

    KAUST Repository

    Himmelberger, Scott

    2012-11-23

    The film thickness of one of the most crystalline and highest performing polymer semiconductors, poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b] thiophene) (PBTTT), is varied in order to determine the effects of interfaces and confinement on the microstructure and performance in organic field effect transistors (OFETs). Crystalline texture and overall film crystallinity are found to depend strongly on film thickness and thermal processing. The angular distribution of crystallites narrows upon both a decrease in film thickness and thermal annealing. These changes in the film microstructure are paired with thin-film transistor characterization and shown to be directly correlated with variations in charge carrier mobility. Charge transport is shown to be governed by film crystallinity in films below 20 nm and by crystalline orientation for thicker films. An optimal thickness is found for PBTTT at which the mobility is maximized in unannealed films and where mobility reaches a plateau at its highest value for annealed films. The effects of confinement on the morphology and charge transport properties of poly(2,5-bis(3-tetradecylthiophen-2-yl) thieno[3,2-b]thiophene) (PBTTT) are studied using quantitative X-ray diffraction and field-effect transistor measurements. Polymer crystallinity is found to limit charge transport in the thinnest films while crystalline texture and intergrain connectivity modulate carrier mobility in thicker films. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Ion-exchange molecularly imprinted polymer for the extraction of negatively charged acesulfame from wastewater samples.

    Science.gov (United States)

    Zarejousheghani, Mashaalah; Schrader, Steffi; Möder, Monika; Lorenz, Pierre; Borsdorf, Helko

    2015-09-11

    Acesulfame is a known indicator that is used to identify the introduction of domestic wastewater into water systems. It is negatively charged and highly water-soluble at environmental pH values. In this study, a molecularly imprinted polymer (MIP) was synthesized for negatively charged acesulfame and successfully applied for the selective solid phase extraction (SPE) of acesulfame from influent and effluent wastewater samples. (Vinylbenzyl)trimethylammonium chloride (VBTA) was used as a novel phase transfer reagent, which enhanced the solubility of negatively charged acesulfame in the organic solvent (porogen) and served as a functional monomer in MIP synthesis. Different molecularly imprinted polymers were synthesized to optimize the extraction capability of acesulfame. The different materials were evaluated using equilibrium rebinding experiments, selectivity experiments and scanning electron microscopy (SEM). The most efficient MIP was used in a molecularly imprinted-solid phase extraction (MISPE) protocol to extract acesulfame from wastewater samples. Using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) analysis, detection and quantification limits were achieved at 0.12μgL(-1) and 0.35μgL(-1), respectively. Certain cross selectivity for the chemical compounds containing negatively charged sulfonamide functional group was observed during selectivity experiments.

  12. Effect of Lattice Distortion on Charge Order in Manganites at Doping x = 0.5

    Institute of Scientific and Technical Information of China (English)

    WANG Hai-Long; TIAN Guang-Shan; LIN Hai-Qing

    2005-01-01

    In the present paper, we continue our investigation on the antiferromagnetic origin of the charge order observed in the half-doped manganese. By introducing a Su-Schrieffer-Heeger (SSH) type of perturbation interaction to the double-exchange Hamiltonian, we calculate again its ground-state phase diagram at filling x = 0.5 by the unrestricted real-space Hartree-Fock approximation method. We find that, as the SSH electron-phonon interaction increases, the charge order parameter decreases to zero rapidly but the CE-type antiferromagnetic order becomes more stable. In other words, the charge order is much more fragile than the CE-type or the Neel-type antiferromagnetic orders under the electron-phonon perturbation. These results support the proposed theory in the recent publications that the charge order in these systems is induced by the antiferromagnetic correlations.

  13. Competition between spin and charge order in a one-dimensional lattice

    Science.gov (United States)

    Talebi, Amir Hossein; Davoudi, Bahman; Rahimitabar, M. Reza

    2017-10-01

    In this paper, we study the presence of competing instabilities in one-dimensional (1D) extended Hubbard model (EHM). Using the extended two-particle self-consistent approximation (ETPSC), we derive the density and interaction dependent crossover diagram for spin and charge density wave fluctuations at arbitrary wave number. We determine the phase transitions of the system by means of spin and charge susceptibilities. We draw the phase diagram which separates different phases of the model for several effective particle densities.

  14. Direct detection of photoinduced charge transfer complexes in polymer fullerene blends

    Science.gov (United States)

    Behrends, Jan; Sperlich, Andreas; Schnegg, Alexander; Biskup, Till; Teutloff, Christian; Lips, Klaus; Dyakonov, Vladimir; Bittl, Robert

    2012-03-01

    We report transient electron paramagnetic resonance (trEPR) measurements with submicrosecond time resolution performed on a polymer:fullerene blend consisting of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) at low temperatures. The trEPR spectrum immediately following photoexcitation reveals signatures of spin-correlated polaron pairs. The pair partners (positive polarons in P3HT and negative polarons in PCBM) can be identified by their characteristic g values. The fact that the polaron pair states exhibit strong non-Boltzmann population unambiguously shows that the constituents of each pair are geminate, i.e., originate from one exciton. We demonstrate that coupled polaron pairs are present even several microseconds after charge transfer and suggest that they embody the intermediate charge transfer complexes that form at the donor/acceptor interface and mediate the conversion from excitons into free charge carriers.

  15. Photoinduced charge carriers in conjugated polymer-fullerene composites studied with light-induced electron-spin resonance

    NARCIS (Netherlands)

    Dyakonov, V.; Zoriniants, G.; Scharber, M.C.; Brabec, C.J.; Janssen, R.A.J.; Hummelen, J.C.

    1999-01-01

    Detailed studies on photoinduced spins in conjugated polymer/fullerene composites using (cw) light-induced electron-spin-resonance (LESR) technique are reported. Two overlapping LESR lines are observed, from positive polarons on the polymer chains and negative charges on the fullerene moieties.

  16. Photoinduced charge carriers in conjugated polymer-fullerene composites studied with light-induced electron-spin resonance

    NARCIS (Netherlands)

    Dyakonov, V.; Zoriniants, G.; Scharber, M.C.; Brabec, C.J.; Janssen, R.A.J.; Hummelen, J.C.

    1999-01-01

    Detailed studies on photoinduced spins in conjugated polymer/fullerene composites using (cw) light-induced electron-spin-resonance (LESR) technique are reported. Two overlapping LESR lines are observed, from positive polarons on the polymer chains and negative charges on the fullerene moieties. Micr

  17. Charge and excitation dynamics in semiconducting polymer layers doped with emitters and charge carrier traps; Ladungstraeger- und Anregungsdynamik in halbleitenden Polymerschichten mit eingemischten Emittern und Ladungstraegerfallen

    Energy Technology Data Exchange (ETDEWEB)

    Jaiser, F.

    2006-06-15

    Light-emitting diodes generate light from the recombination of injected charge carriers. This can be obtained in inorganic materials. Here, it is necessary to produce highly ordered crystalline structures that determine the properties of the device. Another possibility is the utilization of organic molecules and polymers. Based on the versatile organic chemistry, it is possible to tune the properties of the semiconducting polymers already during synthesis. In addition, semiconducting polymers are mechanically flexible. Thus, it is possible to construct flexible, large-area light sources and displays. The first light-emitting diode using a polymer emitter was presented in 1990. Since then, this field of research has grown rapidly up to the point where first products are commercially available. It has become clear that the properties of polymer light-emitting diodes such as color and efficiency can be improved by incorporating multiple components inside the active layer. At the same time, this gives rise to new interactions between these components. While components are often added either to improve the charge transport or to change the emission, it has to made sure that other processes are not influenced in a negative manner. This work investigates some of these interactions and describes them with simple physical models. First, blue light-emitting diodes based on polyfluorene are analyzed. This polymer is an efficient emitter, but it is susceptible to the formation of chemical defects that can not be suppressed completely. These defects form electron traps, but their effect can be compensated by the addition of hole traps. The underlying process, namely the changed charge carrier balance, is explained. In the following, blend systems with dendronized emitters that form electron traps are investigated. The different influence of the insulating shell on the charge and energy transfer between polymer host and the emissive core of the dendrimers is examined. In the

  18. Exotic phase diagram of a cluster charging model of bosons on the kagome lattice

    Science.gov (United States)

    Isakov, Sergei V.; Paramekanti, Arun; Kim, Yong Baek

    2007-12-01

    We study a model of hard-core bosons on the kagome lattice with short-range hopping (t) and repulsive interactions (V) . This model directly maps onto an easy-axis S=1/2 XXZ model on the kagome lattice and is also related, at large V/t , to a quantum dimer model on the triangular lattice. Using quantum Monte Carlo numerics, we map out the phase diagram of this model at half-filling. At T=0 , we show that this model exhibits a superfluid phase at small V/t and an insulating phase at large V/t , separated by a continuous quantum phase transition at Vc/t≈19.8 . The insulating phase at T=0 appears to have no conventional broken symmetries, and is thus a uniform Mott insulator (a “spin liquid” in magnetic language). We characterize this insulating phase as a uniform Z2 fractionalized insulator from the topological order in the ground state and estimate its vison gap. Consistent with this identification, there is no apparent thermal phase transition upon heating the insulator. The insulating phase instead smoothly crosses over into the high temperature paramagnet via an intermediate cooperative paramagnetic regime. We also study the superfluid-to-normal thermal transition for V

  19. Generalized Courant-Snyder theory for charged-particle dynamics in general focusing lattices.

    Science.gov (United States)

    Qin, Hong; Davidson, Ronald C; Chung, Moses; Burby, Joshua W

    2013-09-06

    The Courant-Snyder (CS) theory for one degree of freedom is generalized to the case of coupled transverse dynamics in general linear focusing lattices with quadrupole, skew-quadrupole, dipole, and solenoidal components, as well as torsion of the fiducial orbit and variation of beam energy. The envelope function is generalized into an envelope matrix, and the phase advance is generalized into a 4D sympletic rotation. The envelope equation, the transfer matrix, and the CS invariant of the original CS theory all have their counterparts, with remarkably similar expressions, in the generalized theory.

  20. Order and creep in flux lattices and charge density wave pinned by planar defects.

    Science.gov (United States)

    Petković, Aleksandra; Nattermann, Thomas

    2008-12-31

    The influence of randomly distributed point impurities and planar defects on the order and transport in type-II superconductors and related systems is considered theoretical. For random planar defects of identical orientation, the flux line lattice exhibits a new glassy phase with diverging shear and tilt modulus, a transverse Meissner effect, large sample to sample fluctuations of the susceptibility, and an exponential decay of translational long range order. The flux creep resistivity for currents J parallel to the defects is p(J) to approximately exp-(J0/J)mu with mu = 3/2. Strong disorder enforces an array of dislocations to relax shear

  1. Optimization of thermoelectric performance in semiconducting polymers for understanding charge transport and flexible thermoelectric applications

    Science.gov (United States)

    Glaudell, Anne; Chabinyc, Michael

    2014-03-01

    Organic electronic materials have been widely considered for a variety of energy conversion applications, from photovoltaics to LEDs. Only very recently have organic materials been considered for thermoelectric applications - converting between temperature gradients and electrical potential. The intrinsic disorder in semiconducting polymers leads to an inherently low thermal conductivity, a key parameter in thermoelectric performance. The ability to solution deposit on flexible substrates opens up niche applications including personal cooling and conformal devices. Here work is presented on the electrical conductivity and thermopower of thin film semiconducting polymers, including P3HT and PBTTT-C14. Thermoelectric properties are explored over a wide range of conductivities, from nearly insulating to beyond 100 S/cm, enabled by employing different doping mechanisms, including molecular charge-transfer doping with F4TCNQ and vapor doping with a fluoroalkyl trichlorosilane (FTS). Temperature-dependent measurements suggest competing charge transport mechanisms, likely due to the mixed ordered/disordered character of these polymers. These results show promise for organic materials for thermoelectric applications, and recent results on thin film devices will also be presented.

  2. Characterization and dynamic charge dependent modeling of conducting polymer trilayer bending

    Science.gov (United States)

    Farajollahi, Meisam; Sassani, Farrokh; Naserifar, Naser; Fannir, Adelyne; Plesse, Cédric; Nguyen, Giao T. M.; Vidal, Frédéric; Madden, John D. W.

    2016-11-01

    Trilayer bending actuators are charge driven devices that have the ability to function in air and provide large mechanical amplification. The electronic and mechanical properties of these actuators are known to be functions of their charge state making prediction of their responses more difficult when they operate over their full range of deformation. In this work, a combination of state space representation and a two-dimensional RC transmission line model are used to implement a nonlinear time variant model for conducting polymer-based trilayer actuators. Electrical conductivity and Young’s modulus of electromechanically active PEDOT conducting polymer containing films as a function of applied voltage were measured and incorporated into the model. A 16% drop in Young’s modulus and 24 times increase in conductivity are observed by oxidizing the PEDOT. A closed form formulation for radius of curvature of trilayer actuators considering asymmetric and location dependent Young’s modulus and conductivity in the conducting polymer layers is derived and implemented in the model. The nonlinear model shows the capability to predict the radius of curvature as a function of time and position with reasonable consistency (within 4%). The formulation is useful for general trilayer configurations to calculate the radius of curvature as a function of time. The proposed electrochemical modeling approach may also be useful for modeling energy storage devices.

  3. Polymer-Free Carbon Nanotube Thermoelectrics with Improved Charge Carrier Transport and Power Factor

    Energy Technology Data Exchange (ETDEWEB)

    Norton-Baker, Brenna; Ihly, Rachelle; Gould, Isaac E.; Avery, Azure D.; Owczarczyk, Zbyslaw R.; Ferguson, Andrew J.; Blackburn, Jeffrey L.

    2016-12-09

    Semiconducting single-walled carbon nanotubes (s-SWCNTs) have recently attracted attention for their promise as active components in a variety of optical and electronic applications, including thermoelectricity generation. Here we demonstrate that removing the wrapping polymer from the highly enriched s-SWCNT network leads to substantial improvements in charge carrier transport and thermoelectric power factor. These improvements arise primarily from an increase in charge carrier mobility within the s-SWCNT networks because of removal of the insulating polymer and control of the level of nanotube bundling in the network, which enables higher thin-film conductivity for a given carrier density. Ultimately, these studies demonstrate that highly enriched s-SWCNT thin films, in the complete absence of any accompanying semiconducting polymer, can attain thermoelectric power factors in the range of approximately 400 uW m-1K-2, which is on par with that of some of the best single-component organic thermoelectrics demonstrated to date.

  4. Ultrafast charge- and energy-transfer dynamics in conjugated polymer: cadmium selenide nanocrystal blends.

    Science.gov (United States)

    Morgenstern, Frederik S F; Rao, Akshay; Böhm, Marcus L; Kist, René J P; Vaynzof, Yana; Greenham, Neil C

    2014-02-25

    Hybrid nanocrystal-polymer systems are promising candidates for photovoltaic applications, but the processes controlling charge generation are poorly understood. Here, we disentangle the energy- and charge-transfer processes occurring in a model system based on blends of cadmium selenide nanocrystals (CdSe-NC) with poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) using a combination of time-resolved absorption and luminescence measurements. The use of different capping ligands (n-butylamine, oleic acid) as well as thermal annealing allows tuning of the polymer-nanocrystal interaction. We demonstrate that energy transfer from MDMO-PPV to CdSe-NCs is the dominant exciton quenching mechanism in nonannealed blends and occurs on ultrafast time scales (<1 ps). Upon thermal annealing electron transfer becomes competitive with energy transfer, with a transfer rate of 800 fs independent of the choice of the ligand. Interestingly, we find hole transfer to be much less efficient than electron transfer and to extend over several nanoseconds. Our results emphasize the importance of tuning the organic-nanocrystal interaction to achieve efficient charge separation and highlight the unfavorable hole-transfer dynamics in these blends.

  5. Charged hydrophilic polymer brushes and their relevance for understanding marine biofouling.

    Science.gov (United States)

    Yandi, Wetra; Mieszkin, Sophie; di Fino, Alessio; Martin-Tanchereau, Pierre; Callow, Maureen E; Callow, James A; Tyson, Lyndsey; Clare, Anthony S; Ederth, Thomas

    2016-07-01

    The resistance of charged polymers to biofouling was investigated by subjecting cationic (PDMAEMA), anionic (PSPMA), neutral (PHEMA-co-PEG10MA), and zwitterionic (PSBMA) brushes to assays testing protein adsorption; attachment of the marine bacterium Cobetia marina; settlement and adhesion strength of zoospores of the green alga Ulva linza; settlement of barnacle (Balanus amphitrite and B. improvisus) cypris larvae; and field immersion tests. Several results go beyond the expected dependence on direct electrostatic attraction; PSPMA showed good resistance towards attachment of C. marina, low settlement and adhesion of U. linza zoospores, and significantly lower biofouling than on PHEMA-co-PEG10MA or PSBMA after a field test for one week. PDMAEMA showed potential as a contact-active anti-algal coating due to its capacity to damage attached spores. However, after field testing for eight weeks, there were no significant differences in biofouling coverage among the surfaces. While charged polymers are unsuitable as antifouling coatings in the natural environment, they provide valuable insights into fouling processes, and are relevant for studies due to charging of nominally neutral surfaces.

  6. Analytical methods for describing charged particle dynamics in general focusing lattices using generalized Courant-Snyder theory

    CERN Document Server

    Qin, Hong; Burby, J W; Chung, Moses

    2015-01-01

    The dynamics of charged particles in general linear focusing lattices with quadrupole, skew-quadrupole, dipole, and solenoidal components, as well as torsion of the fiducial orbit and variation of beam energy is parameterized using a generalized Courant-Snyder (CS) theory, which extends the original CS theory for one degree of freedom to higher dimensions. The envelope function is generalized into an envelope matrix, and the phase advance is generalized into a 4D symplectic rotation, or an U(2) element. The 1D envelope equation, also known as the Ermakov-Milne-Pinney equation in quantum mechanics, is generalized to an envelope matrix equation in higher dimensions. Other components of the original CS theory, such as the transfer matrix, Twiss functions, and CS invariant (also known as the Lewis invariant) all have their counterparts, with remarkably similar expressions, in the generalized theory. The gauge group structure of the generalized theory is analyzed. By fixing the gauge freedom with a desired symmetr...

  7. Confronting fluctuations of conserved charges in central nuclear collisions at the LHC with predictions from Lattice QCD

    CERN Document Server

    Braun-Munzinger, P.; Redlich, K.; Stachel, J.

    2016-01-01

    We construct net baryon number and strangeness susceptibilities as well as correlations between electric charge, strangeness and baryon number from experimental data on the particle production yields at midrapidity of the ALICE Collaboration at CERN. The data were taken in central Pb-Pb collisions at $\\sqrt{s_{\\rm NN}}$~=~2.76~TeV and cover one unit of rapidity. We show that the resulting fluctuations and correlations are consistent with Lattice QCD results at the chiral crossover pseudocritical temperature $T_{c} \\simeq$ 155 MeV. This agreement lends strong support to the assumption that the fireball created in these collisions is of thermal origin and exhibits characteristic properties expected in QCD at the transition from the quark gluon plasma to the hadronic phase. Since Lattice QCD calculations are performed at a baryochemical potential of $\\mu_{B}$ = 0, the comparisons with LHC data are the most direct due to the vanishing baryon transport to midrapidity at these high energies.

  8. Origin and impact of recombination via charge transfer excitons in polymer/fullerene solar cells

    Science.gov (United States)

    Hallermann, Markus; da Como, Enrico; Feldmann, Jochen

    2010-03-01

    To further advance the performances of organic photovoltaic cells a thorough understanding of loss mechanisms in polymer/fullerene blends is mandatory. Recombination via charge transfer excitons (CTEs) appears to be a fundamental loss, potentially impacting the open circuit voltage (VOC) and the short circuit current (ISC) of cells. We unravel the origin of CTEs forming in polymer/fullerene blends and discuss their importance in recombination processes considering binding energy [1], polymer conformation [2], and energetic position. CTE photoluminescence (PL) is observed in material combinations such as P3HT and PPV blended with fullerene acceptors. By combining electron microscopy and PL spectroscopy, we show that CTE recombination is only slightly influenced by the mesoscopic morphology, whereas strongly by the polymer chain conformation [2]. By shifting the orbital energies of the fullerene, we tune the CTE PL characteristics. High energy CTE emission results in cells with a beneficial increase in VOC. On the other hand, high energy CTE emission leads to a more efficient recombination impacting directly the ISC. The results highlight a fundamental limit in the efficiency of organic solar cells with CTE recombination. [1] Hallermann et al. APL 2008 [2] Hallermann et al. AFM 2009

  9. Electrophoresis of charged polymers: Simulation and scaling in a lattice model of reptation

    Science.gov (United States)

    Barkema, G. T.; Marko, J. F.; Widom, B.

    1994-06-01

    We report numerical results on the repton model of Rubinstein [Phys. Rev. Lett. 59, 1946 (1987)] as adapted by Duke [Phys. Rev. Lett. 62, 2877 (1989)] as a model for the gel electrophoresis of DNA. We describe an efficient algorithm with which we have simulated chains of N reptons with N several hundred in some instances. The diffusion coefficient D in the absence of an external electric field is obtained for NLeeuwen and Kooiman [Physica A 184, 79 (1992)]. The drift velocity v in a static field of variable strength E is obtained for various N and NE up to N=30 when NE is as small as 0.01 and up to N=400 when NE is as large as 20. We find that v has a finite, nonzero limit as N-->∞ at fixed E and that this limit is proportional to ||E||E, in accord with the conclusions of Duke, Semenov, and Viovy [Phys. Rev. Lett. 69, 3260 (1992)] for a different but related model. In a scaling limit in which N-->∞ and E-->0 the drift velocity in the repton model is fitted well by the formula N2v=NE[(1/3)2+(2NE/5)2]1/2 for all values of the scaling variable NE. We present a scaling analysis complementary to that of Duke, Semenov, and Viovy with which we rationalize the ||E||E behavior of the limiting drift velocity.

  10. Miscibility of nifedipine and hydrophilic polymers as measured by (1)H-NMR spin-lattice relaxation.

    Science.gov (United States)

    Aso, Yukio; Yoshioka, Sumie; Miyazaki, Tamaki; Kawanishi, Tohru; Tanaka, Kazuyuki; Kitamura, Satoshi; Takakura, Asako; Hayashi, Takashi; Muranushi, Noriyuki

    2007-08-01

    The miscibility of a drug with excipients in solid dispersions is considered to be one of the most important factors for preparation of stable amorphous solid dispersions. The purpose of the present study was to elucidate the feasibility of (1)H-NMR spin-lattice relaxation measurements to assess the miscibility of a drug with excipients. Solid dispersions of nifedipine with the hydrophilic polymers poly(vinylpyrrolidone) (PVP), hydroxypropylmethylcellulose (HPMC) and alpha,beta-poly(N-5-hydroxypentyl)-L-aspartamide (PHPA) with various weight ratios were prepared by spray drying, and the spin-lattice relaxation decay of the solid dispersions in a laboratory frame (T(1) decay) and in a rotating frame (T(1rho) decay) were measured. T(1rho) decay of nifedipine-PVP solid dispersions (3 : 7, 5 : 5 and 7 : 3) was describable with a mono-exponential equation, whereas T(1rho) decay of nifedipine-PHPA solid dispersions (3 : 7, 4 : 6 and 5 : 5) was describable with a bi-exponential equation. Because a mono-exponential T(1rho) decay indicates that the domain sizes of nifedipine and polymer in solid dispersion are less than several nm, it is speculated that nifedipine is miscible with PVP but not miscible with PHPA. All the nifedipine-PVP solid dispersions studied showed a single glass transition temperature (T(g)), whereas two glass transitions were observed for the nifedipine-PHPA solid dispersion (3 : 7), thus supporting the above speculation. For nifedipine-HPMC solid dispersions (3 : 7 and 5 : 5), the miscibility of nifedipine and HPMC could not be determined by DSC measurements due to the lack of obviously evident T(g). In contrast, (1)H-NMR spin-lattice relaxation measurements showed that nifedipine and HPMC are miscible, since T(1rho) decay of the solid dispersions (3 : 7, 5 : 5 and 7 : 3) was describable with a mono-exponential equation. These results indicate that (1)H-NMR spin-lattice relaxation measurements are useful for assessing the miscibility of a drug and an

  11. Influence of intensity on the steady and transient state space-charge fields in photorefractive polymers

    Institute of Scientific and Technical Information of China (English)

    袁保红; 孙秀冬; 姜永远; 周忠祥; 姚凤凤; 李焱

    2002-01-01

    We have proven theoretically that there are sublinear, linear and superlinear relations between the response ratesand total incident intensity for different cases of traps in photorefractive polymer materials. These relations wereobserved in inorganic photorefractive crystals many years ago. Also, the steady-state space-charge field is a functionof the total incident intensity, which has also been found in inorganic photorefractive crystals. We have measured therelations of the steady-state diffraction efficiency and the response rate with respect to the total incident intensity in thephotorefractive composite consisting of the polymer (N-vinylcarbazole) (PVK) doped with 4,4'-n-pentylcyanobiphenyl(5CB) and C60. The results obtained show that the composite belongs to the case of low trap density.

  12. Unified Description of Charge-Carrier Mobilities in Disordered Semiconducting Polymers

    Science.gov (United States)

    Pasveer, W. F.; Cottaar, J.; Tanase, C.; Coehoorn, R.; Bobbert, P. A.; Blom, P. W.; de Leeuw, D. M.; Michels, M. A.

    2005-05-01

    From a numerical solution of the master equation for hopping transport in a disordered energy landscape with a Gaussian density of states, we determine the dependence of the charge-carrier mobility on temperature, carrier density, and electric field. Experimental current-voltage characteristics in devices based on semiconducting polymers are excellently reproduced with this unified description of the mobility. At room temperature it is mainly the dependence on carrier density that plays an important role, whereas at low temperatures and high fields the electric field dependence becomes important. Omission in the past of the carrier-density dependence has led to an underestimation of the hopping distance and the width of the density of states in these polymers.

  13. Large and broadband piezoelectricity in smart polymer-foam space-charge electrets

    Science.gov (United States)

    Neugschwandtner, G. S.; Schwödiauer, R.; Vieytes, M.; Bauer-Gogonea, S.; Bauer, S.; Hillenbrand, J.; Kressmann, R.; Sessler, G. M.; Paajanen, M.; Lekkala, J.

    2000-12-01

    Charged closed-cell microporous polypropylene foams are shown to exhibit piezoelectric resonance modes in the dielectric function, coupled with a large anisotropy in the electromechanical and elastic material properties. Strong direct and converse dynamic piezoelectricity with a piezoelectric d33 coefficient of 140 pC/N at 600 kHz is identified. The piezoelectric d33 coefficient exceeds that of the ferroelectric polymer polyvinylidene fluoride by a factor of 5 and compares favorably with ferroelectric ceramics. Applications of similar concepts should provide a broad class of easily fabricated "soft" piezoelectric materials.

  14. Calculation of the (liquid + liquid) equilibrium of solutions of hyperbranched polymers with the lattice-cluster theory combined with an association model

    Energy Technology Data Exchange (ETDEWEB)

    Zeiner, T. [Technical University of Dortmund, Lehrstuhl fuer Fluidverfahrenstechnik, Emil-Figge Str. 70, 44227 Dortmund (Germany); Browarzik, C. [Technical University of Berlin, Institut fuer Prozess- und Verfahrenstechnik (TK7), Fachgebiet Thermodynamik und thermische Verfahrenstechnik, Strasse des 17, Juni 135, 10623 Berlin (Germany); Browarzik, D., E-mail: dieter.browarzik@chemie.uni-halle.de [Martin-Luther University Halle-Wittenberg, Institut fuer Chemie/Physikalische Chemie, 06099 Halle (Germany); Enders, S. [Technical University of Berlin, Institut fuer Prozess- und Verfahrenstechnik (TK7), Fachgebiet Thermodynamik und thermische Verfahrenstechnik, Strasse des 17, Juni 135, 10623 Berlin (Germany)

    2011-12-15

    Highlights: > The (liquid + liquid) equilibrium of hyperbranched polyester solutions is calculated. > The solvents are n-alkanes, propan-1-ol, and butan-1-ol. > The lattice-cluster theory is combined with a chemical association model. > The solvent molecules are assumed to be linear chains of segments. > The calculations agree reasonably well with the experimental data. - Abstract: The (liquid + liquid) equilibrium of solutions of hyperbranched polyesters is calculated with the lattice-cluster theory (LCT) combined with a chemical association model. The considered solvents are n-alkanes as well as propan-1-ol and butan-1-ol. The structure of the solvents is also considered in the framework of the LCT, assuming the solvent molecules as linear chains of several segments. For polymer solutions with the non-associating n-alkanes only the self association of the hyperbranched polymer molecules has to be considered by the chemical association lattice model (CALM). For the solutions of the type alcohol + hyperbranched polymer additionally the cross association is taken into account by a modified version of the extended chemical association lattice model (ECALM). The association effects are proved to influence strongly the phase equilibrium. Calculating the cloud-point curve and the critical point the polydispersity of the polymer samples is neglected. There is a reasonable agreement of the calculated curves with the experimental data taken from the literature.

  15. Frequency domain photon migration measurements of dense monodisperse charged lattices and analysis using solutions of Ornstein Zernike equations.

    Science.gov (United States)

    Dali, Sarabjyot S; Sevick-Muraca, Eva M

    2012-11-15

    Isotropic scattering coefficient measurements were made of monodisperse polystyrene lattices of two different diameters of 144 nm and 223 nm and at volume fractions ranging from 0.15 to 0.22, using frequency domain photon migration measurements at wavelengths of 660, 685, 785 and 828 nm. The isotropic scattering coefficient measurements were shown to be sensitive to the changing ionic strength (0.5-4 mM, NaCl equiv.) of the dispersions exhibiting hindered scattering owing to structure at the lowest ionic strength values. Monte Carlo simulations and numerical solution of the Ornstein Zernike equations were used to compute isotropic scattering coefficients for comparison to measured values. The interaction potential was modeled as a hard sphere Yukawa potential and the Hypernetted Chain closure was used to solve the OZ equation. Effective particle charges were found after renormalization of the bare particle charge and used to predict the isotropic scattering coefficient. The model data were found to follow similar trends as experimental measurements. The refractive index of the particles has found to be an important factor for predicting experimental isotropic scattering coefficient values. Published by Elsevier Inc.

  16. Photonic Bandgap Properties of Atom-lattice Photonic Crystals in Polymer

    Institute of Scientific and Technical Information of China (English)

    REN Lin; WANG Dian; SUN Gui-ting; NIU Li-gang; YANG Han; SONG Jun-feng

    2011-01-01

    The present paper covers the various photonic crystals(PhCs) structures mimicking real atom-lattice structures in electronic crystals by using the femtosecond laser-induced two-photon photopolymerization of SU-8 resin. The bandgap properties were investigated by varying the crystal orientations in <111>, <110> and <100> of diamond-lattice PhCs. lhe photonic stop gaps were present at λ=3.88 μm in <111> direction, λ=4.01 μtm in <110> direction and λ=5.30 μm in <100> direction, respectively. In addition, defects were introduced in graphite-lattice PhCs and the strong localization of photons in this structure with defects at λ=5 μm was achieved. All the above work shows the powerful capability of femtosecond laser fabrication in manufacturing various complicated threedimensional photonic crystals and of controlling photons by inducing defects in the PhCs samples.

  17. The role of emissive charge transfer states in two polymer-fullerene organic photovoltaic blends : tuning charge photogeneration through the use of processing additives

    NARCIS (Netherlands)

    Clarke, Tracey M.; Peet, Jeff; Lungenschmied, Christoph; Drolet, Nicolas; Lu, Xinhui; Ocko, Benjamin M.; Mozer, Attila J.; Loi, Maria Antonietta

    2014-01-01

    The role of charge transfer (CT) states in organic photovoltaic systems has been debated in the recent literature. In this paper the device performances of two structurally analogous polymers PDTSiTTz (also known as KP115) and PCPDTTTz blended with PCBM are investigated, focusing on the effect the p

  18. The role of ionic functionality on charge injection processes in conjugated polymers and fullerenes

    Science.gov (United States)

    Weber, Christopher David

    Understanding the fundamental chemistry of conjugated polymers and fullerenes has been the subject of intense research for the last three decades, with the last ten years seeing increased research toward the application of these materials into functional organic electronic devices such as organic photovoltaic devices (OPVs). This field has seen significant advances is cell efficiency in just the last few years (to >10%), in large part due to the development of new donor and acceptor materials, the fine tuning of fabrication parameters to control material nanostructure, as well as the introduction of new interfacial materials such as ionically functionalized conjugated polymers, also known as conjugated polyelectrolytes (CPEs). This dissertation aims to further understand the fundamental chemistry associated with charge injection processes in CPEs and ionically functionalized fullerenes. The role of ionic functionality on electrochemical, chemical, and interfacial charge injection processes is explored. The results presented demonstrate the use of ionic functionality to control the spatial doping profile of a bilayer structure of anionically and cationically functionalized CPEs to fabricate a p-n junction (Chapter II). The role of ionic functionality on chemical charge injection processes is explored via the reaction of polyacetylene and polythiophene based CPEs with molecular oxygen (Chapters III and IV). The results show the dramatic effect of ionic functionality, as well as the specific role of the counterion, on the photooxidative stability of CPEs. The control of reaction pathway via counterion charge density is also explored (Chapter IV) and shows a continuum of reaction pathways based on the charge density of the counter cation. Finally, the role of ionic functionality on interfacial charge injection processes in a functional OPV is explored using a cationically functionalized fullerene derivative (Chapters V and VI). Cell performance increases due to an

  19. Universal crossover of the charge carrier fluctuation mechanism in different polymer/carbon nanotubes composites

    Energy Technology Data Exchange (ETDEWEB)

    Barone, C., E-mail: cbarone@unisa.it; Mauro, C.; Pagano, S. [Dipartimento di Fisica “E.R. Caianiello” and CNR-SPIN Salerno, Università di Salerno, I-84084 Fisciano, Salerno (Italy); Landi, G.; Neitzert, H. C. [Dipartimento di Ingegneria Industriale, Università di Salerno, I-84084 Fisciano, Salerno (Italy)

    2015-10-05

    Carbon nanotubes added to polymer and epoxy matrices are compounds of interest for applications in electronics and aerospace. The realization of high-performance devices based on these materials can profit from the investigation of their electric noise properties, as this gives a more detailed insight of the basic charge carriers transport mechanisms at work. The dc and electrical noise characteristics of different polymer/carbon nanotubes composites have been analyzed from 10 to 300 K. The results suggest that all these systems can be regarded as random resistive networks of tunnel junctions formed by adjacent carbon nanotubes. However, in the high-temperature regime, contributions deriving from other possible mechanisms cannot be separated using dc information alone. A transition from a fluctuation-induced tunneling process to a thermally activated regime is instead revealed by electric noise spectroscopy. In particular, a crossover is found from a two-level tunneling mechanism, operating at low temperatures, to resistance fluctuations of a percolative network, in the high-temperature region. The observed behavior of 1/f noise seems to be a general feature for highly conductive samples, independent on the type of polymer matrix and on the nanotube density.

  20. Charging dynamics of a polymer due to electron irradiation: A simultaneous scattering-transport model and preliminary results

    Institute of Scientific and Technical Information of China (English)

    Cao Meng; Wang Fang; Liu Jing; Zhang Hai-Bo

    2012-01-01

    We present a novel numerical model and simulate preliminarily the charging process of a polymer subjected to electron irradiation of several 10 keV.The model includes the simultaneous processes of electron scattering and ambipolar transport and the influence of a self-consistent electric field on the scattering distribution of electrons.The dynamic spatial distribution of charges is obtained and validated by existing experimental data.Our simulations show that excess negative charges are concentrated near the edge of the electron range.However,the formed region of high charge density may extend to the surface and bottom of a kapton sample,due to the effects of the electric field on electron scattering and charge transport,respectively.Charge trapping is then demonstrated to significantly influence the charge motion.The charge distribution can be extended to the bottom as the trap density decreases.Charge accumulation is therefore balanced by the appearance and increase of leakage current.Accordingly,our model and numerical simulation provide a comprehensive insight into the charging dynamics of a polymer irradiated by electrons in the complex space environment.

  1. Long-lived charge carrier dynamics in polymer/quantum dot blends and organometal halide perovskites

    Science.gov (United States)

    Nagaoka, Hirokazu

    Solution-processable semiconductors offer a potential route to deploy solar panels on a wide scale, based on the possibility of reduced manufacturing costs by using earth-abundant materials and inexpensive production technologies, such as inkjet or roll-to-roll printing. Understanding the fundamental physics underlying device operation is important to realize this goal. This dissertation describes studies of two kinds of solar cells: hybrid polymer/PbS quantum dot solar cells and organometal halide perovskite solar cells. Chapter two discusses details of the experimental techniques. Chapter three and four explore the mechanisms of charge transfer and energy transfer spectroscopically, and find that both processes contribute to the device photocurrent. Chapter four investigates the important question of how the energy level alignment of quantum dot acceptors affects the operation of hybrid polymer/quantum dot solar cells, by making use of the size-tunable energy levels of PbS quantum dots. We observe that long-lived charge transfer yield is diminished at larger dot sizes as the energy level offset at the polymer/quantum dot interface is changed through decreasing quantum confinement using a combination of spectroscopy and device studies. Chapter five discusses the effects of TiO2 surface chemistry on the performance of organometal halide perovskite solar cells. Specifically, chapter five studies the effect of replacing the conventional TiO2 electrode with Zr-doped TiO2 (Zr-TiO2). We aim to explore the correlation between charge carrier dynamics and device studies by incorporating zirconium into TiO2. We find that, compared to Zr-free controls, solar cells employing Zr-TiO2 give rise to an increase in overall power conversion efficiency, and a decrease in hysteresis. We also observe longer carrier lifetimes and higher charge carrier densities in devices on Zr-TiO2 electrodes at microsecond times in transient photovoltage experiments, as well as at longer persistent

  2. Further evidence of nuclear reactions in the Pd/D lattice: emission of charged particles.

    Science.gov (United States)

    Szpak, Stanislaw; Mosier-Boss, Pamela A; Gordon, Frank E

    2007-06-01

    Almost two decades ago, Fleischmann and Pons reported excess enthalpy generation in the negatively polarized Pd/D-D2O system, which they attributed to nuclear reactions. In the months and years that followed, other manifestations of nuclear activities in this system were observed, viz. tritium and helium production and transmutation of elements. In this report, we present additional evidence, namely, the emission of highly energetic charged particles emitted from the Pd/D electrode when this system is placed in either an external electrostatic or magnetostatic field. The density of tracks registered by a CR-39 detector was found to be of a magnitude that provides undisputable evidence of their nuclear origin. The experiments were reproducible. A model based upon electron capture is proposed to explain the reaction products observed in the Pd/D-D2O system.

  3. Charge Transfer Fluorescence and 34 nm Exciton Diffusion Length in Polymers with Electron Acceptor End Traps.

    Science.gov (United States)

    Zaikowski, Lori; Mauro, Gina; Bird, Matthew; Karten, Brianne; Asaoka, Sadayuki; Wu, Qin; Cook, Andrew R; Miller, John R

    2015-06-18

    Photoexcitation of conjugated poly-2,7-(9,9-dihexylfluorene) polyfluorenes with naphthylimide (NI) and anthraquinone (AQ) electron-acceptor end traps produces excitons that form charge transfer states at the end traps. Intramolecular singlet exciton transport to end traps was examined by steady state fluorescence for polyfluorenes of 17-127 repeat units in chloroform, dimethylformamide (DMF), tetrahydrofuran (THF), and p-xylene. End traps capture excitons and form charge transfer (CT) states at all polymer lengths and in all solvents. The CT nature of the end-trapped states is confirmed by their fluorescence spectra, solvent and trap group dependence, and DFT descriptions. Quantum yields of CT fluorescence are as large as 46%. This strong CT emission is understood in terms of intensity borrowing. Energies of the CT states from onsets of the fluorescence spectra give the depths of the traps which vary with solvent polarity. For NI end traps, the trap depths are 0.06 (p-xylene), 0.13 (THF), and 0.19 eV (CHCl3). For AQ, CT fluorescence could be observed only in p-xylene where the trap depth is 0.27 eV. Quantum yields, emission energies, charge transfer energies, solvent reorganization, and vibrational energies were calculated. Fluorescence measurements on chains >100 repeat units indicate that end traps capture ∼50% of the excitons, and that the exciton diffusion length is LD = 34 nm, which is much larger than diffusion lengths reported in polymer films or than previously known for diffusion along isolated chains. The efficiency of exciton capture depends on chain length but not on trap depth, solvent polarity, or which trap group is present.

  4. Preparation and characterization of polymer composites based on charge-transfer complex of phenothiazine–iodine in polystyrene

    Indian Academy of Sciences (India)

    R A Singh; R K Gupta; S K Singh

    2005-08-01

    Polymer composites based on charge-transfer complex of phenothiazine and iodine with polystyrene have been prepared in different weight ratios and characterized by FTIR, XRD, mechanical, microstructure and electrical properties (d.c. as well as a.c.). These composites show semiconducting behaviour as the conductivity increases with increasing temperature. Low percolation threshold (10% wt CTC) has been found indicating that processable conducting polymers with improved mechanical properties can be prepared by this method.

  5. Reservoir induced topological order and quantized charge pumps in open lattice models with interactions

    Science.gov (United States)

    Linzner, Dominik; Koster, Malte; Grusdt, Fabian; Fleischhauer, Michael

    2016-05-01

    Since the discovery of the quantum Hall effect, topological states of matter have attracted the attention of scientists in many fields of physics. By now there is a rather good understanding of topological order in closed, non-interacting systems. In contrast the extension to open systems in particular with interactions is entirely in its infancy. Recently there have been advances in characterizing topology in reservoir driven systems without interactions, but the topological invariants introduced lack a clear physical interpretation and are restricted to non-interacting systems. We consider a one-dimensional interacting topological system whose dynamics is entirely driven by reservoir couplings. By slowly tuning these couplings periodically in time we realize an open-system analogue of the Thouless charge pump that proves to be robust against unitary and non-unitary perturbations. Making use of this Thouless pump we introduce a topological invariant, which is applicable to interacting systems. Finally we propose a conceptual detection scheme that translates the open-system topological invariant into the context of a well understood closed system.

  6. Nitric Oxide Detection with Glassy Carbon Electrodes Coated with Charge-different Polymer Films

    Directory of Open Access Journals (Sweden)

    Jianping Lei

    2005-04-01

    Full Text Available Trace amounts of nitric oxide (NO have been determined in aqueous phosphate buffersolutions (pH=7.4 by using a glassy carbon electrode coated with three charge-different polymerfilms. The glassy carbon electrode was coated first with negatively charged Nafion film containingtetrakis(pentafluorophenylporphyrin iron(III chloride (Fe(IIITPFPP as the NO oxidation catalyst,and then with positively charged poly(acrylamide-co-diallyldimethylammonium chloride (PADDAand with neutral poly(dimethylsiloxane (silicone at the outermost layer. This polymer-coatedelectrode showed an excellent selectivity towards NO against possible concomitants in blood such asnitrite, ascorbic acid, uric acid, and dopamine. All current ratios between each concomitant and NOat the cyclic voltammogram was in 10-3 ~ 10-4. This type of electrode showed a detection limit of80 nM for NO. It was speculated from the electrochemical study in methanol that high-valent oxoiron(IV of Fe(TPFPP participated in the catalytic oxidation of NO.

  7. Ultrafast dynamics of charge carrier photogeneration and geminate recombination in conjugated polymer:fullerene solar cells

    Science.gov (United States)

    Müller, J. G.; Lupton, J. M.; Feldmann, J.; Lemmer, U.; Scharber, M. C.; Sariciftci, N. S.; Brabec, C. J.; Scherf, U.

    2005-11-01

    We investigate the nature of ultrafast exciton dissociation and carrier generation in acceptor-doped conjugated polymers. Using a combination of two-pulse femtosecond spectroscopy with photocurrent detection, we compare the exciton dissociation and geminate charge recombination dynamics in blends of two conjugated polymers, MeLPPP [methyl-substituted ladder-type poly( p -phenylene)] and MDMO-PPV [poly(2-methoxy,5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene], with the electron accepting fullerene derivative PCBM [1-(3-methoxycarbonyl)-propyl-1-phenyl- (6,6)C61 ]. This technique allows us to distinguish between free charge carriers and Coulombically bound polaron pairs. Our results highlight the importance of geminate pair recombination in photovoltaic devices, which limits the device performance. The comparison of different materials allows us to address the dependence of geminate recombination on the film morphology directly at the polymer:fullerene interface. We find that in the MeLPPP:PCBM blend exciton dissociation generates Coulombically bound geminate polaron pairs with a high probability for recombination, which explains the low photocurrent yield found in these samples. In contrast, in the highly efficient MDMO-PPV:PCBM blend the electron transfer leads to the formation of free carriers. The anisotropy dynamics of electronic transitions from neutral and charged states indicate that polarons in MDMO-PPV relax to delocalized states in ordered domains within 500fs . The results suggest that this relaxation enlarges the distance of carrier separation within the geminate pair, lowering its binding energy and favoring full dissociation. The difference in geminate pair recombination concurs with distinct dissociation dynamics. The electron transfer is preceded by exciton migration towards the PCBM sites. In MeLPPP:PCBM the exciton migration time decays smoothly with increasing PCBM concentration, indicating a trap-free exciton hopping. In MDMO-PPV:PCBM, however

  8. Entanglements in Marginal Solutions: A Means of Tuning Pre-Aggregation of Conjugated Polymers with Positive Implications for Charge Transport

    KAUST Repository

    Hu, Hanlin

    2015-06-17

    The solution-processing of conjugated polymers, just like commodity polymers, is subject to solvent and molecular weight-dependent solubility, interactions and chain entanglements within the polymer, all of which can influence the crystallization and microstructure development in semi-crystalline polymers and consequently affect charge transport and optoelectronic properties. Disentanglement of polymer chains in marginal solvents was reported to work via ultrasonication, facilitating the formation of photophysically ordered polymer aggregates. In this contribution, we explore how a wide range of technologically relevant solvents and formulations commonly used in organic electronics influence chain entanglement and the aggregation behaviour of P3HT using a combination of rheological and spectrophotometric measurements. The specific viscosity of the solution offers an excellent indication of the degree of entanglements in the solution, which is found to be related to the solubility of P3HT in a given solvent. Moreover, deliberately disentangling the solution in the presence of solvophobic driving forces, leads consistently to formation of photophysically visible aggregates which is indicative of local and perhaps long range order in the solute. We show for a broad range of solvents and molecular weights that disentanglement ultimately leads to significant ordering of the polymer in the solid state and a commensurate increase in charge transport properties. In doing so we demonstrate a remarkable ability to tune the microstructure which has important implications for transport properties. We discuss its potential implications in the context of organic photovoltaics.

  9. Charge-regulation phase transition on surface lattices of titratable sites adjacent to electrolyte solutions: An analog of the Ising antiferromagnet in a magnetic field

    Science.gov (United States)

    Shore, Joel D.; Thurston, George M.

    2015-12-01

    We report a charge-patterning phase transition on two-dimensional square lattices of titratable sites, here regarded as protonation sites, placed in a low-dielectric medium just below the planar interface between this medium and a salt solution. We calculate the work-of-charging matrix of the lattice with use of a linear Debye-Hückel model, as input to a grand-canonical partition function for the distribution of occupancy patterns. For a large range of parameter values, this model exhibits an approximate inverse cubic power-law decrease of the voltage produced by an individual charge, as a function of its in-lattice separation from neighboring titratable sites. Thus, the charge coupling voltage biases the local probabilities of proton binding as a function of the occupancy of sites for many neighbors beyond the nearest ones. We find that even in the presence of these longer-range interactions, the site couplings give rise to a phase transition in which the site occupancies exhibit an alternating, checkerboard pattern that is an analog of antiferromagnetic ordering. The overall strength W of this canonical charge coupling voltage, per unit charge, is a function of the Debye length, the charge depth, the Bjerrum length, and the dielectric coefficients of the medium and the solvent. The alternating occupancy transition occurs above a curve of thermodynamic critical points in the (p H-p K ,W ) plane, the curve representing a charge-regulation analog of variation of the Néel temperature of an Ising antiferromagnet as a function of an applied, uniform magnetic field. The analog of a uniform magnetic field in the antiferromagnet problem is a combination of p H-p K and W , and 1 /W is the analog of the temperature in the antiferromagnet problem. We use Monte Carlo simulations to study the occupancy patterns of the titratable sites, including interactions out to the 37th nearest-neighbor category (a distance of √{74 } lattice constants), first validating simulations

  10. Versatile Approach to Access the Low Temperature Thermodynamics of Lattice Polymers and Proteins

    Science.gov (United States)

    Wüst, Thomas; Landau, David P.

    2009-05-01

    We show that Wang-Landau sampling, combined with suitable Monte Carlo trial moves, provides a powerful method for both the ground state search and the determination of the density of states for the hydrophobic-polar (HP) protein model and the interacting self-avoiding walk (ISAW) model for homopolymers. We obtain accurate estimates of thermodynamic quantities for HP sequences with >100 monomers and for ISAWs up to >500 monomers. Our procedure possesses an intrinsic simplicity and overcomes the limitations inherent in more tailored approaches making it interesting for a broad range of protein and polymer models.

  11. Supramolecular ionics: electric charge partition within polymers and other non-conducting solids

    Directory of Open Access Journals (Sweden)

    FERNANDO GALEMBECK

    2001-12-01

    Full Text Available Electrostatic phenomena in insulators have been known for the past four centuries, but many related questions are still unanswered, for instance: which are the charge-bearing species in an electrified organic polymer, how are the charges spatially distributed and which is the contribution of the electrically charged domains to the overall polymer properties? New scanning probe microscopies were recently introduced, and these are suitable for the mapping of electric potentials across a solid sample thus providing some answers for the previous questions. In this work, we report results obtained with two of these techniques: scanning electric potential (SEPM and electric force microscopy (EFM. These results were associated to images acquired by using analytical electron microscopy (energy-loss spectroscopy imaging in the transmission electron microscope, ESI-TEM for colloid polymer samples. Together, they show domains with excess electric charges (and potentials extending up to hundreds of nanometers and formed by large clusters of cations or anions, reaching supramolecular dimensions. Domains with excess electric charge were also observed in thermoplastics as well as in silica, polyphosphate and titanium oxide particles. In the case of thermoplastics, the origin of the charges is tentatively assigned to their tribochemistry, oxidation followed by segregation or the Mawell-Wagner-Sillars and Costa Ribeiro effects.A eletrificação de sólidos é conhecida há quatro séculos, mas há muitas questões importantes sobre este assunto, ainda não respondidas: por exemplo, quais são as espécies portadoras de cargas em um polímero isolante eletrificado, como estas cargas estão espacialmente distribuídas e qual é a contribuição destas cargas para as propriedades do polímero? Técnicas microscópicas introduzidas recentemente são apropriadas para o mapeamento de potenciais elétricos ao longo de uma superfície sólida, portanto podem responder a

  12. Ferroic ordering and charge-spin-lattice order coupling in Gd doped Fe3O4 nanoparticles

    Science.gov (United States)

    Laha, Suvra; Abdelhamid, Ehab; Palihawadana Arachchige, Maheshika; Dixit, Ambesh; Lawes, Gavin; Naik, Vaman; Naik, Ratna

    Rare earth doped spinels have been extensively studied for their potential applications in magneto-optical recording and as MRI contrast agents. In the present study, we have investigated the effect of gadolinium doping (1-5 at.%) on the magnetic and dielectric properties of Fe3O4nanoparticles synthesized by the chemical co-precipitation method. The structure and morphology of the as-synthesized gadolinium doped Fe3O4(Gd-Fe3O4) nanoparticles were characterized by XRD, SEM and TEM, and the magnetic properties were measured by a Quantum Design physical property measurement system. We find that the penetration of excess Gd3+ ions into Fe3O4 spinel matrix significantly influences the average crystallite size and saturation magnetization in Gd-Fe3O4. The average crystallite size, estimated from XRD using Scherrer equation, increases with increasing Gd doping percentage and the saturation magnetization drops monotonically with excess Gd3+ ions. Interestingly, Gd- Fe3O4develops enhanced ferroelectric ordering at low temperatures. The details of the temperature dependent dielectric, ferroelectric and magnetocapacitance measurements to understand the onset of charge-spin-lattice coupling in Gd-Fe3O4 system will be presented.

  13. Confronting fluctuations of conserved charges in central nuclear collisions at the LHC with predictions from Lattice QCD

    Directory of Open Access Journals (Sweden)

    P. Braun-Munzinger

    2015-07-01

    Full Text Available We construct net baryon number and strangeness susceptibilities as well as correlations between electric charge, strangeness and baryon number from experimental data at midrapidity of the ALICE Collaboration at CERN. The data were taken in central Pb–Pb collisions at sNN=2.76 TeV and cover one unit of rapidity. The resulting fluctuations and correlations are consistent with Lattice QCD results at the chiral crossover pseudocritical temperature Tc≃155 MeV. This agreement lends strong support to the assumption that the fireball created in these collisions is of thermal origin and exhibits characteristic properties expected in QCD at the transition from the quark gluon plasma to the hadronic phase. The volume of the fireball for one unit of rapidity at Tc is found to exceed 3000 fm3. A detailed discussion on uncertainties in the temperature and volume of the fireball is presented. The results are linked to pion interferometry measurements and predictions from percolation theory.

  14. Competition between deformability and charge transport in semiconducting polymers for flexible and stretchable electronics

    Energy Technology Data Exchange (ETDEWEB)

    Printz, Adam D.; Lipomi, Darren J., E-mail: dlipomi@ucsd.edu [Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448 (United States)

    2016-06-15

    The primary goal of the field concerned with organic semiconductors is to produce devices with performance approaching that of silicon electronics, but with the deformability—flexibility and stretchability—of conventional plastics. However, an inherent competition between deformability and charge transport has long been observed in these materials, and achieving the extreme (or even moderate) deformability implied by the word “plastic” concurrently with high charge transport may be elusive. This competition arises because the properties needed for high carrier mobilities—e.g., rigid chains in π-conjugated polymers and high degrees of crystallinity in the solid state—are antithetical to deformability. On the device scale, this competition can lead to low-performance yet mechanically robust devices, or high-performance devices that fail catastrophically (e.g., cracking, cohesive failure, and delamination) under strain. There are, however, some observations that contradict the notion of the mutual exclusivity of electronic and mechanical performances. These observations suggest that this problem may not be a fundamental trade-off, but rather an inconvenience that may be negotiated by a logical selection of materials and processing conditions. For example, the selection of the poly(3-alkylthiophene) with a critical side-chain length—poly(3-heptylthiophene) (n = 7)—marries the high deformability of poly(3-octylthiophene) (n = 8) with the high electronic performance (as manifested in photovoltaic efficiency) of poly(3-hexylthiophene) (n = 6). This review explores the relationship between deformability and charge transport in organic semiconductors. The principal conclusions are that reducing the competition between these two parameters is in fact possible, with two demonstrated routes being: (1) incorporation of softer, insulating material into a stiffer, semiconducting material and (2) increasing disorder in a highly ordered film, but not

  15. Yielding and flow of cellulose microfibril dispersions in the presence of a charged polymer.

    Science.gov (United States)

    de Kort, Daan W; Veen, Sandra J; Van As, Henk; Bonn, Daniel; Velikov, Krassimir P; van Duynhoven, John P M

    2016-05-25

    The shear flow of microfibrillated cellulose dispersions is still not wholly understood as a consequence of their multi-length-scale heterogeneity. We added carboxymethyl cellulose, a charged polymer, that makes cellulose microfibril dispersions more homogeneous at the submicron and macro scales. We then compared the yielding and flow behavior of these dispersions to that of typical thixotropic yield-stress fluids. Despite the apparent homogeneity of the dispersions, their flow velocity profiles in cone-plate geometry, as measured by rheo-MRI velocimetry, differ strongly from those observed for typical thixotropic model systems: the viscosity across the gap is not uniform, despite a flat stress field across the gap. We describe these velocity profiles with a nonlocal model, and attribute the non-locality to persistent micron-scale structural heterogeneity.

  16. Verification of the dispersive charge transport in a hydrazone:polycarbonate molecularly doped polymer.

    Science.gov (United States)

    Tyutnev, Andrey P; Saenko, Vladimir S; Pozhidaev, Evgenii D; Kolesnikov, Vladislav A

    2009-03-18

    We report results of specially planned experiments intended to verify the dispersive character of the charge carrier transport in polycarbonate molecularly doped with hydrazone at 30 wt% loading, using for this purpose samples specifically featuring a well-defined plateau on a linear-linear plot. For this purpose we propose a new variant of the time-of-flight technique which allows easy changing of the generation zone width from about 0.5 µm (surface excitation) through intermediate values to full sample thickness (bulk excitation). To achieve this, we use electron pulses of 3-50 keV energy rather than traditional light pulses provided by lasers. Experimental results corroborated by numerical calculations uniquely prove that carrier transport in this molecularly doped polymer is dispersive, with the dispersion parameter equal to 0.75. Nevertheless, the mobility field dependence follows the famous Poole-Frenkel law.

  17. Photo-induced charge transfer and relaxation of persistent charge carriers in polymer/nanocrystal composites for applications in hybrid solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Heinemann, Marc Daniel; Zutz, Folker; Kolny-Olesiak, Joanna; Borchert, Holgert; Riedel, Ingo; Parisi, Juergen [University of Oldenburg, Department of Physics, Energy and Semiconductor Research Laboratory, Oldenburg (Germany); Maydell, Karsten von [EWE Research Center for Energy Technology, Oldenburg (Germany)

    2009-12-09

    The photo-induced charge transfer and the dynamics of persistent charge carriers in blends of semiconducting polymers and nanocrystals are investigated. Regioregular poly(3-hexylthiophene) (P3HT) is used as the electron donor material, while the acceptor moiety is established by CdSe nanocrystals (nc-CdSe) prepared via colloidal synthesis. As a reference system, organic blends of P3HT and [6,6]-phenyl C{sub 61}-butyric acid methyl ester (PCBM) are studied as well. The light-induced charge transfer between P3HT and the acceptor materials is studied by photoluminescence (PL), photo-induced absorption (PIA) and light-induced electron spin resonance spectroscopy (LESR). Compared to neat P3HT samples, both systems show an intensified formation of polarons in the polymer upon photo-excitation, pointing out successful separation of photogenerated charge carriers. Additionally, relaxation of the persistent charge carriers is investigated, and significant differences are found between the hybrid composite and the purely organic system. While relaxation, reflected in the transient signal decay of the polaron signal, is fast in the organic system, the hybrid blends exhibit long-term persistence. The appearance of a second, slow recombination channel indicates the existence of deep trap states in the hybrid system, which leads to the capture of a large fraction of charge carriers. A change of polymer conformation due to the presence of nc-CdSe is revealed by low temperature LESR measurements and microwave saturation techniques. The impact of the different recombination behavior on the photovoltaic efficiency of both systems is discussed. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  18. Organic integrated circuits for information storage based on ambipolar polymers and charge injection engineering

    Science.gov (United States)

    Dell'Erba, Giorgio; Luzio, Alessandro; Natali, Dario; Kim, Juhwan; Khim, Dongyoon; Kim, Dong-Yu; Noh, Yong-Young; Caironi, Mario

    2014-04-01

    Ambipolar semiconducting polymers, characterized by both high electron (μe) and hole (μh) mobility, offer the advantage of realizing complex complementary electronic circuits with a single semiconducting layer, deposited by simple coating techniques. However, to achieve complementarity, one of the two conduction paths in transistors has to be suppressed, resulting in unipolar devices. Here, we adopt charge injection engineering through a specific interlayer in order to tune injection into frontier energy orbitals of a high mobility donor-acceptor co-polymer. Starting from field-effect transistors with Au contacts, showing a p-type unbalanced behaviour with μh = 0.29 cm2/V s and μe = 0.001 cm2/V s, through the insertion of a caesium salt interlayer with optimized thickness, we obtain an n-type unbalanced transistor with μe = 0.12 cm2/V s and μh = 8 × 10-4 cm2/V s. We applied this result to the development of the basic pass-transistor logic building blocks such as inverters, with high gain and good noise margin, and transmission-gates. In addition, we developed and characterized information storage circuits like D-Latches and D-Flip-Flops consisting of 16 transistors, demonstrating both their static and dynamic performances and thus the suitability of this technology for more complex circuits such as display addressing logic.

  19. Transparent and Electrically Conductive Carbon Nanotube-Polymer Nanocomposite Materials for Electrostatic Charge Dissipation

    Science.gov (United States)

    Dervishi, E.; Biris, A. S.; Biris, A. R.; Lupu, D.; Trigwell, S.; Miller, D. W.; Schmitt, T.; Buzatu, D. A.; Wilkes, J. G.

    2006-01-01

    In recent years, nanocomposite materials have been extensively studied because of their superior electrical, magnetic, and optical properties and large number of possible applications that range from nano-electronics, specialty coatings, electromagnetic shielding, and drug delivery. The aim of the present work is to study the electrical and optical properties of carbon nanotube(CNT)-polymer nanocomposite materials for electrostatic charge dissipation. Single and multi-wall carbon nanotubes were grown by catalytic chemical vapor deposition (CCVD) on metal/metal oxide catalytic systems using acetylene or other hydrocarbon feedstocks. After the purification process, in which amorphous carbon and non-carbon impurities were removed, the nanotubes were functionalized with carboxylic acid groups in order to achieve a good dispersion in water and various other solvents. The carbon nanostructures were analyzed, both before and after functionalization by several analytical techniques, including microscopy, Raman spectroscopy, and X-Ray photoelectron spectroscopy. Solvent dispersed nanotubes were mixed (1 to 7 wt %) into acrylic polymers by sonication and allowed to dry into 25 micron thick films. The electrical and optical properties of the films were analyzed as a function of the nanotubes' concentration. A reduction in electrical resistivity, up to six orders of magnitude, was measured as the nanotubes' concentration in the polymeric films increased, while optical transparency remained 85 % or higher relative to acrylic films without nanotubes.

  20. Field enhanced charge carrier reconfiguration in electronic and ionic coupled dynamic polymer resistive memory

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Junhui; Thomson, Douglas J; Freund, Michael S [Department of Electrical and Computer Engineering, University of Manitoba, Winnipeg, MB (Canada); Pilapil, Matt; Pillai, Rajesh G; Aminur Rahman, G M, E-mail: thomson@ee.umanitoba.ca, E-mail: michael_freund@umanitoba.ca [Department of Chemistry, University of Manitoba, Winnipeg, MB (Canada)

    2010-04-02

    Dynamic resistive memory devices based on a conjugated polymer composite (PPy{sup 0}DBS{sup -}Li{sup +} (PPy: polypyrrole; DBS{sup -}: dodecylbenzenesulfonate)), with field-driven ion migration, have been demonstrated. In this work the dynamics of these systems has been investigated and it has been concluded that increasing the applied field can dramatically increase the rate at which information can be 'written' into these devices. A conductance model using space charge limited current coupled with an electric field induced ion reconfiguration has been successfully utilized to interpret the experimentally observed transient conducting behaviors. The memory devices use the rising and falling transient current states for the storage of digital states. The magnitude of these transient currents is controlled by the magnitude and width of the write/read pulse. For the 500 nm length devices used in this work an increase in 'write' potential from 2.5 to 5.5 V decreased the time required to create a transient conductance state that can be converted into the digital signal by 50 times. This work suggests that the scaling of these devices will be favorable and that 'write' times for the conjugated polymer composite memory devices will decrease rapidly as ion driving fields increase with decreasing device size.

  1. An insight into the mechanism of charge-transfer of hybrid polymer:ternary/quaternary chalcopyrite colloidal nanocrystals

    Directory of Open Access Journals (Sweden)

    Parul Chawla

    2014-08-01

    Full Text Available In this work, we have demonstrated the structural and optoelectronic properties of the surface of ternary/quaternary (CISe/CIGSe/CZTSe chalcopyrite nanocrystallites passivated by tri-n-octylphosphine-oxide (TOPO and tri-n-octylphosphine (TOP and compared their charge transfer characteristics in the respective polymer: chalcopyrite nanocomposites by dispersing them in poly(3-hexylthiophene polymer. It has been found that CZTSe nanocrystallites due to their high crystallinity and well-ordered 3-dimensional network in its pristine form exhibit a higher steric- and photo-stability, resistance against coagulation and homogeneity compared to the CISe and CIGSe counterparts. Moreover, CZTSe nanocrystallites display efficient photoluminescence quenching as evident from the high value of the Stern–Volmer quenching constant (KSV and eventually higher charge transfer efficiency in their respective polymer P3HT:CZTSe composites. We modelled the dependency of the charge transfer from the donor and the charge separation mechanism across the donor–acceptor interface from the extent of crystallinity of the chalcopyrite semiconductors (CISe/CIGSe/CZTSe. Quaternary CZTSe chalcopyrites with their high crystallinity and controlled morphology in conjunction with regioregular P3HT polymer is an attractive candidate for hybrid solar cells applications.

  2. An insight into the mechanism of charge-transfer of hybrid polymer:ternary/quaternary chalcopyrite colloidal nanocrystals.

    Science.gov (United States)

    Chawla, Parul; Singh, Son; Sharma, Shailesh Narain

    2014-01-01

    In this work, we have demonstrated the structural and optoelectronic properties of the surface of ternary/quaternary (CISe/CIGSe/CZTSe) chalcopyrite nanocrystallites passivated by tri-n-octylphosphine-oxide (TOPO) and tri-n-octylphosphine (TOP) and compared their charge transfer characteristics in the respective polymer: chalcopyrite nanocomposites by dispersing them in poly(3-hexylthiophene) polymer. It has been found that CZTSe nanocrystallites due to their high crystallinity and well-ordered 3-dimensional network in its pristine form exhibit a higher steric- and photo-stability, resistance against coagulation and homogeneity compared to the CISe and CIGSe counterparts. Moreover, CZTSe nanocrystallites display efficient photoluminescence quenching as evident from the high value of the Stern-Volmer quenching constant (K SV) and eventually higher charge transfer efficiency in their respective polymer P3HT:CZTSe composites. We modelled the dependency of the charge transfer from the donor and the charge separation mechanism across the donor-acceptor interface from the extent of crystallinity of the chalcopyrite semiconductors (CISe/CIGSe/CZTSe). Quaternary CZTSe chalcopyrites with their high crystallinity and controlled morphology in conjunction with regioregular P3HT polymer is an attractive candidate for hybrid solar cells applications.

  3. Carbon Nanotube/Conductive Additive/Space Durable Polymer Nanocomposite Films for Electrostatic Charge Dissipation

    Science.gov (United States)

    Smith, Joseph G., Jr.; Watson, Kent A.; Delozier, Donavon M.; Connell, John W.

    2003-01-01

    Thin film membranes of space environmentally stable polymeric materials possessing low color/solar absorptivity (alpha) are of interest for potential applications on Gossamer spacecraft. In addition to these properties, sufficient electrical conductivity is required in order to dissipate electrostatic charge (ESC) build-up brought about by the charged orbital environment. One approach to achieve sufficient electrical conductivity for ESC mitigation is the incorporation of single wall carbon nanotubes (SWNTs). However, when the SWNTs are dispersed throughout the polymer matrix, the nanocomposite films tend to be significantly darker than the pristine material resulting in a higher alpha. The incorporation of conductive additives in combination with a decreased loading level of SWNTs is one approach for improving alpha while retaining conductivity. Taken individually, the low loading level of conductive additives and SWNTs is insufficient in achieving the percolation level necessary for electrical conductivity. When added simultaneously to the film, conductivity is achieved through a synergistic effect. The chemistry, physical, and mechanical properties of the nanocomposite films will be presented.

  4. Interplay Between Side Chain Pattern, Polymer Aggregation, and Charge Carrier Dynamics in PBDTTPD:PCBM Bulk-Heterojunction Solar Cells

    KAUST Repository

    Dyer-Smith, Clare

    2015-05-01

    Poly(benzo[1,2-b:4,5-b′]dithiophene–alt–thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymer donors with linear side-chains yield bulk-heterojunction (BHJ) solar cell power conversion efficiencies (PCEs) of about 4% with phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor, while a PBDTTPD polymer with a combination of branched and linear substituents yields a doubling of the PCE to 8%. Using transient optical spectroscopy it is shown that while the exciton dissociation and ultrafast charge generation steps are not strongly affected by the side chain modifications, the polymer with branched side chains exhibits a decreased rate of nongeminate recombination and a lower fraction of sub-nanosecond geminate recombination. In turn the yield of long-lived charge carriers increases, resulting in a 33% increase in short circuit current (J sc). In parallel, the two polymers show distinct grazing incidence X-ray scattering spectra indicative of the presence of stacks with different orientation patterns in optimized thin-film BHJ devices. Independent of the packing pattern the spectroscopic data also reveals the existence of polymer aggregates in the pristine polymer films as well as in both blends which trap excitons and hinder their dissociation.

  5. Polymer lattices as mechanically tunable 3-dimensional photonic crystals operating in the infrared

    Energy Technology Data Exchange (ETDEWEB)

    Chernow, V. F., E-mail: vchernow@caltech.edu [Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125 (United States); Alaeian, H. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States); Dionne, J. A. [Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States); Greer, J. R. [Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125 (United States); The Kavli Nanoscience Institute, California Institute of Technology, Pasadena, California 91125 (United States)

    2015-09-07

    Broadly tunable photonic crystals in the near- to mid-infrared region could find use in spectroscopy, non-invasive medical diagnosis, chemical and biological sensing, and military applications, but so far have not been widely realized. We report the fabrication and characterization of three-dimensional tunable photonic crystals composed of polymer nanolattices with an octahedron unit-cell geometry. These photonic crystals exhibit a strong peak in reflection in the mid-infrared that shifts substantially and reversibly with application of compressive uniaxial strain. A strain of ∼40% results in a 2.2 μm wavelength shift in the pseudo-stop band, from 7.3 μm for the as-fabricated nanolattice to 5.1 μm when strained. We found a linear relationship between the overall compressive strain in the photonic crystal and the resulting stopband shift, with a ∼50 nm blueshift in the reflection peak position per percent increase in strain. These results suggest that architected nanolattices can serve as efficient three-dimensional mechanically tunable photonic crystals, providing a foundation for new opto-mechanical components and devices across infrared and possibly visible frequencies.

  6. Effect of intrachain sulfonic acid dopants on the solid-state charge mobility of a model radical polymer

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Holly; Wang, Yucheng; Boudouris, Bryan W., E-mail: boudouris@purdue.edu

    2015-02-27

    Radical polymers are an emerging class of non-conjugated, charge-conducting macromolecules that are capable of transporting charge through localized oxidation–reduction (redox) reactions that occur at the stable radical groups present as the pendant groups of the macromolecular chains. The chemical nature and oxidation state of these pendant radical groups are critical to the charge transporting abilities of radical polymers in the solid state. To date, however, the control of this chemistry has been limited to external oxidizing agents, and the concept of intramolecular dopants has not been explored fully. To this end, we have synthesized poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate)-co-poly(vinylsulfonic acid sodium salt) (PTMA-co-PVS). Then, electron paramagnetic resonance spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy are implemented to evaluate the exact chemical nature of the pendant groups as a function of the PVS intramolecular dopants and exposure of the materials to external oxidation reactions. We correlate these changes in pendant group chemistry to charge transport ability, and we establish that the inclusion of a moderate amount of PVS dopants can improve the solid-state hole mobility of the material. Conversely, a large amount of sulfonic acidic dopants can be detrimental to the transport of the polymer relative to the homopolymer PTMA. Therefore, refinement of pendant group chemistry and careful addition of intramolecular dopants can enhance the solid-state transport ability of a radical polymer system. These fundamental principles, in turn, provide a vital foothold by which to optimize the solid-state charge transporting ability of current and next-generation radical polymer designs. - Highlights: • Sulfonic acid groups are copolymerized within the backbone of radical polymer chain. • Addition of the sulfonic acid groups alters the pendant group oxidation state. • Exact oxidation states are

  7. Mécanismes d'écoulement des charges à la surface des polymères granulaires

    Directory of Open Access Journals (Sweden)

    M. Kachi

    2014-09-01

    Full Text Available Les forces électriques s’exerçant sur des polymères granulaires chargés sont mises à profit dans plusieurs processus électrostatiques. La dynamique de charges de surface de ces matériaux est très importante pour ce type de processus. Le but de ce papier est d’analyser l’écoulement des charges à la surface de couches compactes de polymères granulaires, en interprétant les mesures sans contact réalisées par trois sondes de potentiel, de champ et de charge, ayant chacune une taille différente. Des mesures du profile de potentiel à différents instants sont également réalisées afin d’expliquer les différences entre les vitesses de déclin de potentiel, de champ et de charge mesurées par les trois sondes. Les résultats mettent en évidence un écoulement transversal et longitudinal de la charge surfacique.

  8. Charging suppression in focused-ion beam fabrication of visible subwavelength dielectric grating reflector using electron conducting polymer

    KAUST Repository

    Alias, Mohd Sharizal

    2015-08-19

    Nanoscale periodic patterning on insulating materials using focused-ion beam (FIB) is challenging because of charging effect, which causes pattern distortion and resolution degradation. In this paper, the authors used a charging suppression scheme using electron conducting polymer for the implementation of FIB patterned dielectric subwavelength grating (SWG) reflector. Prior to the FIB patterning, the authors numerically designed the optimal structure and the fabrication tolerance for all grating parameters (period, grating thickness, fill-factor, and low refractive index layer thickness) using the rigorous-coupled wave analysis computation. Then, the authors performed the FIB patterning on the dielectric SWG reflector spin-coated with electron conducting polymer for the anticharging purpose. They also performed similar patterning using thin conductive film anticharging scheme (30 nm Cr coating) for comparison. Their results show that the electron conducting polymer anticharging scheme effectively suppressing the charging effect during the FIB patterning of dielectric SWG reflector. The fabricated grating exhibited nanoscale precision, high uniformity and contrast, constant patterning, and complied with fabrication tolerance for all grating parameters across the entire patterned area. Utilization of electron conducting polymer leads to a simpler anticharging scheme with high precision and uniformity for FIB patterning on insulator materials.

  9. Molecular Design and Device Application of Radical Polymers for Improved Charge Extraction in Organic Photovoltaic Cells

    Science.gov (United States)

    2015-07-29

    and voltage-dependence of radical polymer thin films was found to be quite robust; this was despite the lone electron nature of the radical site...respect to many oft-used conjugated polymers . Because of these advantageous properties, radical polymer thin films have been included in a number of...radical polymers is temperature-independent if the radical polymer thin film is in the glassy state. This observation is in direct agreement with the

  10. Organic integrated circuits for information storage based on ambipolar polymers and charge injection engineering

    Energy Technology Data Exchange (ETDEWEB)

    Dell' Erba, Giorgio; Natali, Dario [Center for Nano Science and Technology PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano (Italy); Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano (Italy); Luzio, Alessandro; Caironi, Mario, E-mail: mario.caironi@iit.it, E-mail: yynoh@dongguk.edu [Center for Nano Science and Technology PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano (Italy); Kim, Juhwan; Khim, Dongyoon; Kim, Dong-Yu [Heeger Center for Advanced Materials, School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712 (Korea, Republic of); Noh, Yong-Young, E-mail: mario.caironi@iit.it, E-mail: yynoh@dongguk.edu [Department of Energy and Materials Engineering, Dongguk University, 26 Pil-dong, 3-ga, Jung-gu, Seoul 100-715 (Korea, Republic of)

    2014-04-14

    Ambipolar semiconducting polymers, characterized by both high electron (μ{sub e}) and hole (μ{sub h}) mobility, offer the advantage of realizing complex complementary electronic circuits with a single semiconducting layer, deposited by simple coating techniques. However, to achieve complementarity, one of the two conduction paths in transistors has to be suppressed, resulting in unipolar devices. Here, we adopt charge injection engineering through a specific interlayer in order to tune injection into frontier energy orbitals of a high mobility donor-acceptor co-polymer. Starting from field-effect transistors with Au contacts, showing a p-type unbalanced behaviour with μ{sub h} = 0.29 cm{sup 2}/V s and μ{sub e} = 0.001 cm{sup 2}/V s, through the insertion of a caesium salt interlayer with optimized thickness, we obtain an n-type unbalanced transistor with μ{sub e} = 0.12 cm{sup 2}/V s and μ{sub h} = 8 × 10{sup −4} cm{sup 2}/V s. We applied this result to the development of the basic pass-transistor logic building blocks such as inverters, with high gain and good noise margin, and transmission-gates. In addition, we developed and characterized information storage circuits like D-Latches and D-Flip-Flops consisting of 16 transistors, demonstrating both their static and dynamic performances and thus the suitability of this technology for more complex circuits such as display addressing logic.

  11. Impact of electrostatics on the chemodynamics of highly charged metal-polymer nanoparticle complexes.

    Science.gov (United States)

    Duval, Jérôme F L; Farinha, José Paulo S; Pinheiro, José P

    2013-11-12

    In this work, the impact of electrostatics on the stability constant, the rate of association/dissociation, and the lability of complexes formed between Cd(II), Pb(II), and carboxyl-modified polymer nanoparticles (also known as latex particles) of radius ∼ 50 nm is systematically investigated via electroanalytical measurements over a wide range of pHs and NaNO3 electrolyte concentrations. The corresponding interfacial structure and key electrostatic properties of the particles are independently derived from their electrokinetic response, successfully interpreted using soft particle electrohydrodynamic formalism, and complemented by Förster resonance energy transfer (FRET) analysis. The results underpin the presence of an ∼0.7-1 nm thick permeable and highly charged shell layer at the surface of the polymer nanoparticles. Their electrophoretic mobility further exhibits a minimum versus NaNO3 concentration due to strong polarization of the electric double layer. Integrating these structural and electrostatic particle features with recent theory on chemodynamics of particulate metal complexes yields a remarkable recovery of the measured increase in complex stability with increasing pH and/or decreasing solution salinity. In the case of the strongly binding Pb(II), the discrepancy at pH > 5.5 is unambiguously assigned to the formation of multidendate complexes with carboxylate groups located in the particle shell. With increasing pH and/or decreasing electrolyte concentration, the theory further predicts a kinetically controlled formation of metal complexes and a dramatic loss of their lability (especially for lead) on the time-scale of diffusion toward a macroscopic reactive electrode surface. These theoretical findings are again shown to be in agreement with experimental evidence.

  12. Electrical conductivity, dielectric response and space charge dynamics of an electroactive polymer with and without nanofiller reinforcement

    Science.gov (United States)

    Kochetov, R.; Tsekmes, I. A.; Morshuis, P. H. F.

    2015-07-01

    Electroactive polymers have gained considerable attention over the last 20 years for exhibiting a large displacement in response to electrical stimulation. The promising fields of application include wave energy converters, muscle-like actuators, sensors, robotics, and biomimetics. For an electrical engineer, electroactive polymers can be seen as a dielectric elastomer film or a compliant capacitor with a highly deformable elastomeric medium. If the elastomer is pre-stretched and pre-charged, a reduction of the tensile force lets the elastomer revert to its original form and increases the electrical potential. The light weight of electroactive polymers, low cost, high intrinsic breakdown strength, cyclical way of operation, reliable performance, and high efficiency can be exploited to utilize the elastomeric material as a transducer. The energy storage for a linear dielectric polymer is determined by its relative permittivity and the applied electric field. The latter is limited by the dielectric breakdown strength of the material. Therefore, to generate a high energy density of a flexible capacitor, the film must be used at the voltage level close to the material’s breakdown or inorganic particles with high dielectric permittivity which can be introduced into the polymer matrix. In the present study, silicone-titania elastomer nanocomposites were produced and the influence of nanoparticles on the macroscopic dielectric properties of the neat elastomer including space charge dynamics, complex permittivity, and electrical conductivity, were investigated.

  13. Fluctuations and Correlations of net baryon number, electric charge, and strangeness: A comparison of lattice QCD results with the hadron resonance gas model

    CERN Document Server

    Bazavov, A; DeTar, C E; Ding, H -T; Gottlieb, Steven; Gupta, Rajan; Hegde, P; Heller, Urs; Karsch, F; Laermann, E; Levkova, L; Mukherjee, Swagato; Petreczky, P; Schmidt, Christian; Soltz, R A; Soeldner, W; Sugar, R; Vranas, Pavlos M

    2012-01-01

    We calculate the quadratic fluctuations of net baryon number, electric charge and strangeness as well as correlations among these conserved charges in (2+1)-flavor lattice QCD at zero chemical potential. Results in the continuum limit are obtained using calculations with tree level improved gauge and the highly improved staggered quark (HISQ) actions with almost physical light and strange quark masses at three different values of the lattice cut-off. We compare our results with the hadron resonance gas (HRG) model calculations and find agreement with HRG model results only for temperatures T < 150 MeV. We observe significant deviations in the temperature range 160 MeV < T < 170 MeV and qualitative differences in the behavior of the three conserved charge sectors. At $T \\simeq 160 MeV$ quadratic net baryon number fluctuations in QCD agree with HRG model calculations while, the net electric charge fluctuations in QCD are about 10% smaller and net strangeness fluctuations are about 20% larger. These fin...

  14. The effect of polymer size and charge of molecules on permeation through synovial membrane and accumulation in hyaline articular cartilage.

    Science.gov (United States)

    Sterner, B; Harms, M; Wöll, S; Weigandt, M; Windbergs, M; Lehr, C M

    2016-04-01

    The treatment of joint related diseases often involves direct intra-articular injections. For rational development of novel delivery systems with extended residence time in the joint, detailed understanding of transport and retention phenomena within the joint is mandatory. This work presents a systematic study on the in vitro permeation, penetration and accumulation of model polymers with differing charges and molecular weights in bovine joint tissue. Permeation experiments with bovine synovial membrane were performed with PEG polymers (6-200 kDa) and methylene blue in customized diffusion chambers. For polyethylene glycol, 2-fold (PEG 6 kDa), 3-fold (PEG 10 kDa) and 13-fold (PEG 35 kDa) retention by the synovial membrane in reference to the small molecule methylene blue was demonstrated. No PEG 200 kDa was found in the acceptor in detectable amounts after 48 h. This showed the potential for a distinct extension of joint residence times by increasing molecular weights. In addition, experiments with bovine cartilage tissue were conducted. The ability for positively charged, high molecular weight chitosans and HEMA-Co-TMAP (HCT) polymers (up to 233 kDa) to distribute throughout the entire cartilage matrix was demonstrated. In contrast, a distribution into cartilage was not observed for neutral PEG polymers (6-200 kDa). Furthermore, the positive charge density of different compounds (chitosan, HEMA-Co-TMAP, methylene blue, MSC C1 (neutral NCE) and MSC D1 (positively charged NCE) was found to correlate with their accumulation in bovine cartilage tissue. In summary, the results offer pre-clinical in vitro data, indicating that the modification of molecular size and charge of a substance has the potential to decelerate its clearance through the synovial membrane and to promote accumulation inside the cartilage matrix. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Side chain engineering of fused aromatic thienopyrazine based low band-gap polymers for enhanced charge carrier mobility

    KAUST Repository

    Mondal, Rajib

    2011-01-01

    A strategic side-chain engineering approach leads to the two orders of magnitude enhancement of charge carrier mobility in phenanthrene based fused aromatic thienopyrazine polymers. Hole carrier mobility up to 0.012 cm 2/Vs can be obtained in thin film transistor devices. Polymers were also utilized to fabricate bulk heterojunction photovoltaic devices and the maximum PCE obtained in these OPV\\'s was 1.15%. Most importantly, performances of the devices were correlated with thin morphological analysis performed by atomic force microscopy and grazing incidence X-ray scattering. © 2011 The Royal Society of Chemistry.

  16. Zeta potential and electroosmotic mobility in microfluidic devices fabricated from hydrophobic polymers: 1. The origins of charge.

    Science.gov (United States)

    Tandon, Vishal; Bhagavatula, Sharath K; Nelson, Wyatt C; Kirby, Brian J

    2008-03-01

    This paper combines new experimental data for electrokinetic characterization of hydrophobic polymers with a detailed discussion of the putative origins of charge at water-hydrophobe interfaces. Complexities in determining the origin of charge are discussed in the context of design and modeling challenges for electrokinetic actuation in hydrophobic microfluidic devices with aqueous working fluids. Measurements of interfacial charge are complicated by slip and interfacial water structuring phenomena (see Part 2, this issue). Despite these complexities, it is shown that (i) several hydrophobic materials, such as Teflon and Zeonor, have predictable electrokinetic properties and (ii) electrokinetic data for hydrophobic microfluidic systems is most consistent with the postulate that hydroxyl ion adsorption is the origin of charge.

  17. Photoinduced charge transfer in donor-acceptor (DA) copolymer: fullerene bis-adduct polymer solar cells.

    Science.gov (United States)

    Kang, Tae Eui; Cho, Han-Hee; Cho, Chul-Hee; Kim, Ki-Hyun; Kang, Hyunbum; Lee, Myounghee; Lee, Sunae; Kim, Bongsoo; Im, Chan; Kim, Bumjoon J

    2013-02-01

    Polymer solar cells (PSCs) consisting of fullerene bis-adduct and poly(3-hexylthiophene) (P3HT) blends have shown higher efficiencies than P3HT:phenyl C(61)-butyric acid methyl ester (PCBM) devices, because of the high-lying lowest unoccupied molecular orbital (LUMO) level of the fullerene bis-adducts. In contrast, the use of fullerene bis-adducts in donor-acceptor (DA) copolymer systems typically causes a decrease in the device's performance due to the decreased short-circuit current (J(SC)) and the fill factor (FF). However, the reason for such poor performance in DA copolymer:fullerene bis-adduct blends is not fully understood. In this work, bulk-heterojunction (BHJ)-type PSCs composed of three different electron donors with four different electron acceptors were chosen and compared. The three electron donors were (1) poly[(4,8-bis-(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-2,6-diyl-alt-(5-octylthieno[3,4-c]pyrrole-4,6-dione)-1,3-diyl] (PBDTTPD), (2) poly[(4,8-bis-(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene)-2,6-diyl] (PBDTTT-C), and (3) P3HT polymers. The four electron acceptors were (1) PCBM, (2) indene-C(60) monoadduct (ICMA), (3) indene-C(60) bis-adduct (ICBA), and (4) indene-C(60) tris-adduct (ICTA). To understand the difference in the performance of BHJ-type PSCs for the three different polymers in terms of the choice of fullerene acceptor, the structural, optical, and electrical properties of the blends were measured by the external quantum efficiency (EQE), photoluminescence, grazing incidence X-ray scattering, and transient absorption spectroscopy. We observed that while the molecular packing and optical properties cannot be the main reasons for the dramatic decrease in the PCE of the DA copolymers and ICBA, the value of the driving force for charge transfer (ΔG(CT)) is a key parameter for determining the change in J(SC) and device efficiency in the DA copolymer- and P3HT-based PSCs in

  18. Grafted polymers layers: neutral chains to charged chains; Couches de polymeres greffes: des chaines neutres aux chaines chargees

    Energy Technology Data Exchange (ETDEWEB)

    Mir, Y.

    1995-09-29

    This work concerns an experimental study, by small angle neutrons scattering, of neutral or charged grafted polymers layers structures. The method consisted in exploiting the acknowledges got on neutral brushes, to reach the problem of grafted polyelectrolyte layers. The difficulty of charged layers making has been, until this day, an important obstacle to the experimental study of these systems. It has been partially resolved in the case of sodium sulfonate polystyrene layers, and allowed to study their structure. (N.C.). 72 refs., 74 figs., 24 tabs.

  19. Charge transport in zirconium doped anatase nanowires dye-sensitized solar cells: Trade-off between lattice strain and photovoltaic parameters

    Energy Technology Data Exchange (ETDEWEB)

    Archana, P. S.; Gupta, Arunava [Department of Chemistry, University of Alabama, 250 Hackberry Lane, Shelby hall, Tuscaloosa 35401 Alabama (United States); Yusoff, Mashitah M.; Jose, Rajan, E-mail: rjose@ump.edu.my [Faculty of Industrial Sciences and Technology, Universiti Malaysia Pahang, 26300 Kuantan (Malaysia)

    2014-10-13

    Zirconium (Zr) is doped up to 5 at. % in anatase TiO{sub 2} nanowires by electrospinning and used as working electrode in dye-sensitized solar cells. Variations observed in the photovoltaic parameters were correlated by electrochemical impedance spectroscopy, open circuit voltage decay, and X-ray diffraction measurements. Results show that homovalent substitution of Zr in TiO{sub 2} increased the chemical capacitance and electron diffusion coefficient which in turn decreased charge transport resistance and charge transit time. However, lattice strain due to size mismatch between the Zr{sup 4+} and Ti{sup 4+} ions decreased open circuit voltage and fill factor thereby setting a trade-off between doping concentration and photovoltaic properties.

  20. The effects of nanoparticles and organic additives with controlled dispersion on dielectric properties of polymers: Charge trapping and impact excitation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yanhui, E-mail: huangy12@rpi.edu; Schadler, Linda S. [Department of Material Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Wu, Ke; Ratcliff, Tyree; Lanzillo, Nicholas A.; Breneman, Curt [Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Bell, Michael; Oakes, Andrew; Benicewicz, Brian C. [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208 (United States)

    2016-08-07

    This work presents a comprehensive investigation into the effects of nanoparticles and organic additives on the dielectric properties of insulating polymers using reinforced silicone rubber as a model system. TiO{sub 2} and ZrO{sub 2} nanoparticles (d = 5 nm) were well dispersed into the polymer via a bimodal surface modification approach. Organic molecules with the potential of voltage stabilization were further grafted to the nanoparticle to ensure their dispersion. These extrinsic species were found to provide deep traps for charge carriers and exhibited effective charge trapping properties at a rather small concentration (∼10{sup 17} cm{sup −3}). The charge trapping is found to have the most significant effect on breakdown strength when the electrical stressing time is long enough that most charges are trapped in the deep states. To establish a quantitative correlation between the trap depth and the molecular properties, the electron affinity and ionization energy of each species were calculated by an ab initio method and were compared with the experimentally measured values. The correlation however remains elusive and is possibly complicated by the field effect and the electronic interactions between different species that are not considered in this computation. At high field, a super-linear increase of current density was observed for TiO{sub 2} filled composites and is likely caused by impact excitation due to the low excitation energy of TiO{sub 2} compared to ZrO{sub 2}. It is reasoned that the hot charge carriers with energies greater than the excitation energy of TiO{sub 2} may excite an electron-hole pair upon collision with the NP, which later will be dissociated and contribute to free charge carriers. This mechanism can enhance the energy dissipation and may account for the retarded electrical degradation and breakdown of TiO{sub 2} composites.

  1. The effects of nanoparticles and organic additives with controlled dispersion on dielectric properties of polymers: Charge trapping and impact excitation

    Science.gov (United States)

    Huang, Yanhui; Wu, Ke; Bell, Michael; Oakes, Andrew; Ratcliff, Tyree; Lanzillo, Nicholas A.; Breneman, Curt; Benicewicz, Brian C.; Schadler, Linda S.

    2016-08-01

    This work presents a comprehensive investigation into the effects of nanoparticles and organic additives on the dielectric properties of insulating polymers using reinforced silicone rubber as a model system. TiO2 and ZrO2 nanoparticles (d = 5 nm) were well dispersed into the polymer via a bimodal surface modification approach. Organic molecules with the potential of voltage stabilization were further grafted to the nanoparticle to ensure their dispersion. These extrinsic species were found to provide deep traps for charge carriers and exhibited effective charge trapping properties at a rather small concentration (˜1017 cm-3). The charge trapping is found to have the most significant effect on breakdown strength when the electrical stressing time is long enough that most charges are trapped in the deep states. To establish a quantitative correlation between the trap depth and the molecular properties, the electron affinity and ionization energy of each species were calculated by an ab initio method and were compared with the experimentally measured values. The correlation however remains elusive and is possibly complicated by the field effect and the electronic interactions between different species that are not considered in this computation. At high field, a super-linear increase of current density was observed for TiO2 filled composites and is likely caused by impact excitation due to the low excitation energy of TiO2 compared to ZrO2. It is reasoned that the hot charge carriers with energies greater than the excitation energy of TiO2 may excite an electron-hole pair upon collision with the NP, which later will be dissociated and contribute to free charge carriers. This mechanism can enhance the energy dissipation and may account for the retarded electrical degradation and breakdown of TiO2 composites.

  2. Charge transport effects in field emission from carbon nanotube-polymer composites

    OpenAIRE

    Smith, RC; Carey, JD; Murphy, RJ; Blau, WJ; Coleman, JN; Silva, SRP

    2006-01-01

    Electron field emission measurements have been made on multiwall arc discharge carbon nanotubes embedded in a conjugated polymer host. Electron emission at low nanotube content is observed and attributed to an enhancement of the applied electric field at the polymer/nanotube/vacuum interface where the electron supply through the film is attributed to fluctuation induced tunneling in a disordered percolation network. A high network resistance is attributed to a polymer coating surrounding each...

  3. Interplay of charge, spin, and lattice degrees of freedom in the spectral properties of the one-dimensional Hubbard-Holstein model

    Science.gov (United States)

    Nocera, A.; Soltanieh-ha, M.; Perroni, C. A.; Cataudella, V.; Feiguin, A. E.

    2014-11-01

    We calculate the spectral function of the one-dimensional Hubbard-Holstein model using the time-dependent density matrix renormalization group, focusing on the regime of large local Coulomb repulsion, and away from electronic half-filling. We argue that, from weak to intermediate electron-phonon coupling, phonons interact only with the electronic charge, and not with the spin degrees of freedom. For strong electron-phonon interaction, spinon and holon bands are not discernible anymore and the system is well described by a spinless polaronic liquid. In this regime, we observe multiple peaks in the spectrum with an energy separation corresponding to the energy of the lattice vibrations (i.e., phonons). We support the numerical results by introducing a well controlled analytical approach based on Ogata-Shiba's factorized wave function, showing that the spectrum can be understood as a convolution of three contributions, originating from charge, spin, and lattice sectors. We recognize and interpret these signatures in the spectral properties and discuss the experimental implications.

  4. Understanding the relationship between molecular order and charge transport properties in conjugated polymer based organic blend photovoltaic devices.

    Science.gov (United States)

    Wood, Sebastian; Kim, Jong Soo; James, David T; Tsoi, Wing C; Murphy, Craig E; Kim, Ji-Seon

    2013-08-14

    We report a detailed characterization of the thin film morphology of all-polymer blend devices by applying a combined analysis of physical, chemical, optical, and charge transport properties. This is exemplified by considering a model system comprising poly(3-hexylthiophene) (P3HT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). We show that the interactions between the two conjugated polymer components can be controlled by pre-forming the P3HT into highly ordered nanowire structures prior to blending with F8BT, and by varying the molecular weight of the F8BT. As a result, it is possible to produce films containing highly ordered P3HT with hole mobilities enhanced by three orders of magnitude over the pristine blends. Raman spectroscopy under resonant excitation conditions is used to probe the molecular order of both P3HT and F8BT phases within the blend films and these morphological studies are complemented by measurements of photocurrent generation. The resultant increase in photocurrent is associated with the enhanced charge carrier mobilities. The complementary analytical method demonstrated here is applicable to a wide range of polymer blend systems for all applications where the relationships between morphology and device performance are of interest.

  5. Chiral Spin-Density Wave, Spin-Charge-Chern Liquid, and d+id Superconductivity in 1/4-Doped Correlated Electronic Systems on the Honeycomb Lattice

    Directory of Open Access Journals (Sweden)

    Shenghan Jiang

    2014-09-01

    Full Text Available Recently, two interesting candidate quantum phases—the chiral spin-density wave state featuring anomalous quantum Hall effect and the d+id superconductor—were proposed for the Hubbard model on the honeycomb lattice at 1/4 doping. Using a combination of exact diagonalization, density matrix renormalization group, the variational Monte Carlo method, and quantum field theories, we study the quantum phase diagrams of both the Hubbard model and the t-J model on the honeycomb lattice at 1/4 doping. The main advantage of our approach is the use of symmetry quantum numbers of ground-state wave functions on finite-size systems (up to 32 sites to sharply distinguish different quantum phases. Our results show that for 1≲U/t<40 in the Hubbard model and for 0.1charge-Chern liquid, but not a d+id superconductor. However, in the t-J model, upon increasing J, the system goes through a first-order phase transition at J/t=0.80(2 into the d+id superconductor. Here, the spin-charge-Chern liquid state is a new type of topologically ordered quantum phase with Abelian anyons and fractionalized excitations. Experimental signatures of these quantum phases, such as tunneling conductance, are calculated. These results are discussed in the context of 1/4-doped graphene systems and other correlated electronic materials on the honeycomb lattice.

  6. Interplay of electron hopping and bounded diffusion during charge transport in redox polymer electrodes.

    Science.gov (United States)

    Akhoury, Abhinav; Bromberg, Lev; Hatton, T Alan

    2013-01-10

    Redox polymer electrodes (RPEs) have been prepared both by attachment of random copolymers of hydroxybutyl methacrylate and vinylferrocene (poly(HBMA-co-VF)) to carbon substrates by grafting either "to" or "from" the substrate surfaces, and by impregnation of porous carbon substrates with redox polymer gels of similar composition. An observed linear dependence of peak current on the square root of the applied voltage scan rate in cyclic voltammetry (CV) led to the conclusion that the rate controlling step in the redox process was the diffusive transfer of electrons through the redox polymer layer. The variation in the peak current with increasing concentration of the redox species in the polymer indicated that the electron transport transitioned from bounded diffusion to electron hopping. A modified form of the Blauch-Saveant equation for apparent diffusivity of electrons through a polymer film indicated that bounded diffusion was the dominant mechanism of electron transport in RPEs with un-cross-linked polymer chains at low concentrations of the redox species, but, as the concentration of the redox species increased, electron hopping became more dominant, and was the primary mode of electron diffusion above a certain concentration level of redox species. In the cross-linked polymer gels, bounded diffusion was limited because of the restricted mobility of the polymer chains. Electron hopping was the primary mode of electron diffusion in such systems at all concentrations of the redox species.

  7. Conjugated polymer charge-transfer complexes : A new route to low-bandgap photostable materials

    NARCIS (Netherlands)

    Bakulin, Artem A.; Pshenichnikov, Maxim S.; Van Loosdrecht, Paul H M; Golovnin, Ilya V.; Paraschuk, Dmitry Yu

    2010-01-01

    Polymer solar cells have high potential to convert solar energy into electricity in a cost-effective way. To date, the best polymer solar cells show the efficiency about 5%, and significant efforts are underway to increase their efficiency to the level of practical applications. One of the key strat

  8. Dispersion of iron oxide particles in industrial waters. The influence of polymer structure, ionic charge, and molecular weight

    Energy Technology Data Exchange (ETDEWEB)

    Amjad, Z. [Goodrich (B.F.) Co., Brecksville, OH (United States)

    1999-01-01

    This paper deals with studies on the influence of polymeric and non-polymeric materials on the dispersion of iron oxide particles in aqueous system. The aim of the work was to evaluate the performance of a variety of additives as iron oxide dispersants. The polymers investigated include homopolymers of acrylamide, vinylpyrrolidone, actylic acid, maleic acid, 2-acrylamido-2-methylpropane sulfonic acid, and acrylic acid based copolymers containing a variety of functional groups. It has been found that the addition of low levels of copolymers to the iron oxide suspension has a marked effect in dispersing iron oxide particles. The dispersancy data of several polymers indicate that the performance of the polymer depends upon the functional group, molecular weight, composition, and the ionic charge of the polymer. The results on non-polymeric materials such as polyphosphates, phosphonates, and surfactants show that these additives, compared to copolymers are ineffective as iron oxide dispersants. (orig.) [Deutsch] In dieser Arbeit wird der Einfluss von polymeren und nichtpolymeren Stoffen auf die Dispergierung von Eisenoxidpartikeln in waessrigen Systemen untersucht. Ziel dieser Arbeit war es, die Wirkung verschiedener Additive als Eisenoxiddispergatoren zu bewerten. Die untersuchten Polymere waren homopolymeres Acrylamid, Vinylpyrrolidon, Acrylsaeure, Maleinsaeure, 2-Acrylamido-2-Methylpropansulfonsaeure und Copolymere auf Acrylsaeurebasis mit verschiedenen fuktionellen Gruppen. Die Zugabe von geringen Mengen Copolymeren zur Eisenoxidsuspension hat einen deutlichen Einfluss auf die Dispergierung dieser Partikel. Die Daten zum Dispergierverhalten einiger Polymere zeigen, dass die Wirkung eines Polymers von der fuktionellen Gruppe, dem Molgewicht, der Zusammensetzung und der Ionenladung des Polymers abhaengt. Ergebnisse, die mit nichtpolymeren Substanzen wie Polyphosphaten, Phosphonaten und Tensiden erhalten wurden, zeigen, dass sich diese Additive nicht so gut als

  9. Ionic conductivity of polymer gels deriving from alkali metal ionic liquids and negatively charged polyelectrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Ogihara, Wataru; Yoshizawa, Masahiro; Ohno Hiroyuki [Tokyo University of Agriculture and Technology (Japan). Dept. of Biotechnology; Sun, Jiazeng; Forsyth, M. [Monash University, Clayton (Australia). School of Materials Engineering; MacFarlane, D.R. [Monash University, Clayton (Australia). School of Chemistry

    2004-04-30

    We have prepared polymer gel electrolytes with alkali metal ionic liquids (AMILs) that inherently contain alkali metal ions. The AMIL consisted of sulfate anion, imidazolium cation, and alkali metal cation. AMILs were mixed directly with poly(3-sulfopropyl acrylate) lithium salt or poly(2-acrylamido-2-methylpropanesulfonic acid) lithium salt to form polymer gels. The ionic conductivity of these gels decreased with increasing polymer fraction, as in general ionic liquid/polymer mixed systems. At low polymer concentrations, these gels displayed excellent ionic conductivity of 10{sup -4} to 10{sup -3} S cm{sup -1} at room temperature. Gelation was found to cause little change in the {sup 7}Li diffusion coefficient of the ionic liquid, as measured by pulse-field-gradient NMR. These data strongly suggest that the lithium cation migrates in successive pathways provided by the ionic liquids. (author)

  10. Characterization of Charge-Carrier Transport in Semicrystalline Polymers: Electronic Couplings, Site Energies, and Charge-Carrier Dynamics in Poly(bithiophene- alt -thienothiophene) [PBTTT

    KAUST Repository

    Poelking, Carl

    2013-01-31

    We establish a link between the microscopic ordering and the charge-transport parameters for a highly crystalline polymeric organic semiconductor, poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). We find that the nematic and dynamic order parameters of the conjugated backbones, as well as their separation, evolve linearly with temperature, while the side-chain dynamic order parameter and backbone paracrystallinity change abruptly upon the (also experimentally observed) melting of the side chains around 400 K. The distribution of site energies follows the behavior of the backbone paracrystallinity and can be treated as static on the time scale of a single-charge transfer reaction. On the contrary, the electronic couplings between adjacent backbones are insensitive to side-chain melting and vary on a much faster time scale. The hole mobility, calculated after time-averaging of the electronic couplings, reproduces well the value measured in a short-channel thin-film transistor. The results underline that to secure efficient charge transport in lamellar arrangements of conjugated polymers: (i) the electronic couplings should present high average values and fast dynamics, and (ii) the energetic disorder (paracrystallinity) should be small. © 2013 American Chemical Society.

  11. Charged polymers in the attractive regime: a first order transition from Brownian scaling to four points localization

    CERN Document Server

    Hu, Yueyun; Wouts, Marcel

    2010-01-01

    We study a quenched charged-polymer model, introduced by Garel and Orland in 1988, that reproduces the folding/unfolding transition of biopolymers. We prove that, below the critical inverse temperature, the polymer is delocalized in the sense that: (1) The rescaled trajectory of the polymer converges to the Brownian path; and (2) The partition function remains bounded. At the critical inverse temperature, we show that the maximum time spent at points jumps discontinuously from 0 to a positive fraction of the number of monomers, in the limit as the number of monomers tends to infinity. Finally, when the critical inverse temperature is large, we prove that the polymer collapses in the sense that a large fraction of its monomers live on four adjacent positions, and its diameter grows only logarithmically with the number of the monomers. Our methods also provide some insight into the annealed phase transition and at the transition due to a pulling force; both phase transitions are shown to be discontinuous.

  12. Permeability and charge-dependent adsorption properties of the S-layer lattice from Bacillus coagulans E38-66.

    OpenAIRE

    Sára, M; Pum, D; Sleytr, U B

    1992-01-01

    We investigated the permeability properties of the oblique S-layer lattice from Bacillus coagulans E38-66 after depositing cell wall fragments on a microfiltration membrane, cross-linking the S-layer protein with glutaraldehyde, and degrading the peptidoglycan with lysozyme. Comparative permeability studies on such multilayered S-layer membranes and suspended S-layer vesicles from thermophilic members of the family Bacillaceae with use of the space technique (M. Sára and U. B. Sleytr, J. Bact...

  13. Mass and charge transfer on various relevant scales in polymer electrolyte fuel cells[Dissertation 16991

    Energy Technology Data Exchange (ETDEWEB)

    Freunberger, S. A.

    2007-07-01

    This dissertation is concerned with the development, experimental diagnostics and mathematical modelling and simulation of polymer electrolyte fuel cells (PEFC). The central themes throughout this thesis are the closely interlinked phenomena of mass and charge transfer. In the face of developing a PEFC system for vehicle propulsion these phenomena are scrutinized on a broad range of relevant scales. Starting from the material related level of the membrane and the gas diffusion layer (GDL) we turn to length scales, where structural features of the cell additionally come into play. These are the scale of flow channels and ribs, the single cell and the cell stack followed by the cell, stack, and system development for an automotive power train. In Chapter 3 selected fundamental material models and properties, respectively, are explored that are crucial for the mathematical modelling and simulation of PEFC, as needed in some succeeding parts of this work. First, established mathematical models for mass and charge transfer in the membrane are compared within the framework of the membrane electrode assembly (MEA), which represents the electrochemical unit. Second, reliable values for effective diffusivities in the GDLs which are vital for the simulation of gaseous mass transport are measured. Therefore, a method is developed that allows measuring this quantity both as a function of compression and direction as this is a prerequisite of sophisticated more-dimensional numerical PEFC-models. Besides the cross section of the catalyst layer (CL) mass transfer under channels and ribs is considered as a major source of losses in particular under high load operation. As up to now there have been solely non-validated theoretical investigations, in Chapter 4 an experimental method is developed that is for the first time capable of resolving the current density distribution on the this scale. For this, the electron conductors in the cell are considered as 2-dimensional shunt

  14. Study of charge transport in highly conducting polymers based on a random resistor network

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Liping [Department of Physics, Suzhou University, Suzhou 215006 (China)]. E-mail: lipichow@hotmail.com; Liu Bo [Department of Physics, Suzhou University, Suzhou 215006 (China); Department of Physics, Jiangsu Teachers University of Technology, Changzhou 213001 (China); Li Zhenya [CCAST (World Laboratory), P.O. Box 8730, Beijing 100080 (China) and Department of Physics, Suzhou University, Suzhou 215006 (China)]. E-mail: zyli@suda.edu.cn

    2004-12-06

    Based on a random resistor network (RRN), we study the unusual ac conductivity {sigma}({omega}) of highly conducting polymer such as PF{sub 6} doped polypyrrole. The system is modeled as a composite medium consisting of metallic regions randomly distributed in the amorphous parts. Within the metallic regions, the polymer chains are regularly and densely packed, outside which the poorly arranged chains form amorphous host. The metallic grains are connected by resonance quantum tunneling, which occurs through the strongly localized states in the amorphous media. {sigma}({omega}), calculated from this model, reproduces the main experimental features associated with the metal-insulator transition in these polymers.

  15. Band Bending in Conjugated Polymer Films: Role of Morphology and Implications for Bulk Charge Transport Characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Green, Peter [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Wenderott, J. K. [University of Michigan; Dong, Ban Xuan [University of Michigan

    2017-08-14

    The performance of power conversion devices is impacted by the energy level alignment at the interface between the conjugated polymer and conductive substrate. While band bending has been known to vary between conjugated polymers, we show that the degree of band bending within the same polymer can be just as significant with morphology change. Specifically, a significant band bending effect, studied via Kelvin probe force microscopy (KPFM), was exhibited by poly(3-hexylthiophene) (P3HT) films fabricated using matrix assisted pulsed laser evaporation (MAPLE) in contrast to the conventional spin-cast P3HT films. This finding is associated with a broadening of the density of states (DOS) in the MAPLE-deposited P3HT films, originating from the more disordered structure of the film. These findings, to the best of our knowledge, illustrate for the first time a strong connection between morphology, energy level alignment, and bulk transport in conjugated polymer films.

  16. Ultrafast optical measurements of charge generation and transfer mechanisms of pi-conjugated polymers for solar cell applications

    Science.gov (United States)

    Holt, Joshua Michael

    Current developments in organic solar cells based on donor-acceptor blends require understanding and control of photoinduced charge transfer and electronic state dynamics. In this work the ultrafast dynamics of photoexcitations in pi-conjugated organic semiconductors were studied using a low-intensity, high-repetition rate laser system in the broad mid- to near-infrared (IR) spectral range from 0.25 to 1.1 eV, and a high-intensity, low-repetition rate laser system in the spectral range from 1.2 to 2.5 eV, in the time domain up to 1 ns with 150 fs resolution. We also applied CW photomodulation spectroscopy along with excitation spectrum, modulation frequency sweeps, photoluminescence and electroabsorption to study the excited states of pi-conjugated polymers and acceptor-donor blends. One current drawback to organic solar cell efficiency is negligible absorption in the near infrared spectral range of the solar spectrum. We provide and compare evidence that poly(2-methoxy-5(2'-ethyl)hexoxy-phenylenevinylene) (MEH-PPV) [electron donor] blended with 2,4,7-trinitrofluorenone (TNF) [strong electron acceptor] form a below-gap charge transfer complex (CTC) state that can extend absorption into the near infrared. The transient PA measurements also show that significant charge species are initially photogenerated, a majority of which geminately recombine within 8-10 ps, but the few that escape geminate recombination are subsequently captured in long-lived traps. In addition polarons could be also photogenerated with high efficiency at near-IR excitation, with similar fate. This demonstrates that a CTC state exists below the MEH-PPV polymer optical gap, but with low dissociation efficiency. We compare our results to those in blends of MEH-PPV/C60 where apparently a charge transport pathway to the electrodes is formed and the obtained CTC state has higher dissociation efficiency. The most efficient all-organic photovoltaic (OPV) cells to date (˜6% power conversion efficiency

  17. Soft porous crystal meets TCNQ: charge transfer-type porous coordination polymers

    OpenAIRE

    Shimomura, Satoru; Kitagawa, Susumu

    2011-01-01

    The significant progress of porous coordination polymers (or metal–organic frameworks) has been attracting the attention of a lot of scientists in various disciplines and encouraging their entry into this field. The synergy of diverse scientific senses brings further spread of the chemistry of porous coordination polymers. In this review, we introduced the recent developments in PCPs resulting from the hybridization with TCNQ chemistry. Electronic and structural diversities of TCNQ provide no...

  18. Studies on the antifungal activities of the novel synthesized chelating co-polymer emulsion lattices and their silver complexes

    Directory of Open Access Journals (Sweden)

    Abd-El-Ghaffar M.A.

    2008-01-01

    Full Text Available The novel binary chelating co-polymers of butyl acrylate with itaconic and maleic acids were prepared by emulsion polymerization process. The chelating co-polymers of butyl acrylate-co-itaconic acid (BuA/IA and butyl acrylate-co-maleic acid (BuA/MA and their silver complexes were characterized and identified using IR spectroscopy and differential scanning calorimetry (DSC measurements. The biological activities of these compounds were studied against various types of fungal species. The dose and the rate of leached silver ions were controlled by the type of the co-polymers used and the solubility in the medium. The results provided laboratory support for the concept that the polymers containing chemically bound biocide are useful for controlling microbial growth. The silver uptake by strains of different fungal species was studied to determine their difference in behavior to the antifungal activities of these compounds. The uptake strategy was examined by transmission electron microscopy (TEM.

  19. Unified Description of Charge-Carrier Mobilities in Disordered Semiconducting Polymers

    NARCIS (Netherlands)

    Pasveer, W.F.; Cottaar, J.; Tanase, C.; Coehoorn, R.; Bobbert, P.A.; Blom, P.W.M.; De Leeuw, D.M.; Michels, M.A.J.

    2005-01-01

    From a numerically exact solution of the Master equation for hoppingtransport in a disordered energy landscape with a Gaussian densityof states, we determine the dependence on temperature, carrier density, and electric field of the charge carrier mobility. Experimentalspace-charge limited currents i

  20. Charge transport and vector meson dissociation across the thermal phase transition in lattice QCD with two light quark flavors

    CERN Document Server

    Brandt, Bastian B; Jaeger, Benjamin; Meyer, Harvey B

    2015-01-01

    We compute and analyze correlation functions in the isovector vector channel at vanishing spatial momentum across the deconfinement phase transition in lattice QCD. The simulations are carried out at temperatures $T/T_c=0.156, 0.8, 1.0, 1.25$ and $1.67$ with $T_c\\simeq203$MeV for two flavors of Wilson-Clover fermions with a zero-temperature pion mass of $\\simeq270$MeV. Exploiting exact sum rules and applying a phenomenologically motivated ansatz allows us to determine the spectral function $\\rho(\\omega,T)$ via a fit to the lattice correlation function data. From these results we estimate the electrical conductivity across the deconfinement phase transition via a Kubo formula and find evidence for the dissociation of the $\\rho$ meson by resolving its spectral weight at the available temperatures. We also apply the Backus-Gilbert method as a model-independent approach to this problem. At any given frequency, it yields a local weighted average of the true spectral function. We use this method to compare kinetic ...

  1. The Development of Conductive Nanoporous Chitosan Polymer Membrane for Selective Transport of Charged Molecules

    Directory of Open Access Journals (Sweden)

    Pei-Ru Chen

    2013-01-01

    Full Text Available We present the development of conductive nanoporous CNT/chitosan membrane for charge-selective transport of charged molecules, carboxylfluorescein (CF, substance P, and tumor necrosis factor-alpha (TNF-α. The membrane was made porous and conductive via gelatin nanoparticle leaching technique and addition of carbon nanotubes, respectively. These nanoporous membranes discriminate the diffusion of positive-charged molecules while inhibiting the passage of negative-charged molecules as positive potential was applied. The permeation selectivity of these membranes is reversed by converting the polarity of applied potential into negative. Based on this principle, charged molecules (carboxylfluorescein, substance P, and TNF-α are successfully filtered through these membranes. This system shows 30 times more selective for CF than substance P as positive potential was applied, while 2.5 times more selective for substance P than CF as negative potential was applied.

  2. Nonlinear lattice relaxation of photogenerated charge-transfer excitation in halogen-bridged mixed-valence metal complexes. II. Polaron channel

    Science.gov (United States)

    Mishima, A.; Nasu, K.

    1989-03-01

    The one-dimensional extended Peierls-Hubbard model with half-filled-band electrons is studied in order to clarify the lattice relaxation path of the photogenerated charge-transfer excitation in halogen-bridged mixed-valence metal complexes. The ground and excited states are calculated within mean-field theory for electrons and the adiabatic approximation for phonons. It is concluded that the main origin of the photoinduced absorption is a distant pair of the hole-polaron and the electron-polaron. This distant pair is created not from the ground state of the self-trapped exciton (STE), but from the excited states of the STE through their autodissociation. This is consistent with the experiment on the excitation energy dependence of the photoinduced absorption yield.

  3. Ultrafast photogeneration of charged polarons on conjugated polymer chains in dilute solution

    Science.gov (United States)

    Miranda, Paulo B.; Moses, Daniel; Heeger, Alan J.

    2004-08-01

    Ultrafast photoinduced absorption by infrared-active vibrational modes is used to study the photogeneration of polarons on semiconducting polymer chains in dilute solutions and in solid films of a soluble derivative of poly(para-phenylene vinylene). In dilute solutions, polaron pairs are photogenerated on the conjugated polymer within less than 250fs with quantum efficiencies ϕch˜3% , about one-third of that for solid films of the same polymer. The excitation spectra of ϕch for both solutions and films show that ϕch is weakly dependent on photon energy between 2.2eV (the onset of absorption) and 4.7eV . The recombination dynamics of polarons is very fast and highly dependent on the excitation density for polymer films, but it is significantly slower and less sensitive to pump intensity for the semiconducting polymer in dilute solution. We conclude that the positive and negative polarons on a single chain in solution are typically separated by hundreds of monomer repeat units and that their one-dimensional diffusion along the chain is inhibited by the intervening excitons. This, together with the suppression of interchain recombination, explains the surprisingly slower polaron recombination in isolated chains.

  4. Antimicrobial polymers prepared by ring-opening metathesis polymerization: manipulating antimicrobial properties by organic counterion and charge density variation.

    Science.gov (United States)

    Lienkamp, Karen; Madkour, Ahmad E; Kumar, Kushi-Nidhi; Nüsslein, Klaus; Tew, Gregory N

    2009-11-02

    The synthesis and characterization of a series of poly(oxanorbornene)-based synthetic mimics of antimicrobial peptides (SMAMPs) is presented. In the first part, the effect of different organic counterions on the antimicrobial properties of the SMAMPs was investigated. Unexpectedly, adding hydrophobicity by complete anion exchange did not increase the SMAMPs' antimicrobial activity. It was found by dye-leakage studies that this was due to the loss of membrane activity of these polymers caused by the formation of tight ion pairs between the organic counterions and the polymer backbone. In the second part, the effect of molecular charge density on the biological properties of a SMAMP was investigated. The results suggest that, above a certain charge threshold, neither minimum inhibitory concentration (MIC90) nor hemolytic activity (HC50) is greatly affected by adding more cationic groups to the molecule. A SMAMP with an MIC90 of 4 microg mL(-1) against Staphylococcus aureus and a selectivity (=HC50/MIC90) of 650 was discovered, the most selective SMAMP to date.

  5. Physically adsorbed fullerene layer on positively charged sites on zinc oxide cathode affords efficiency enhancement in inverted polymer solar cell.

    Science.gov (United States)

    Cheng, Yu-Shan; Liao, Sih-Hao; Li, Yi-Lun; Chen, Show-An

    2013-07-24

    We present a novel idea for overcoming the drawback of poor contact between the ZnO cathode and active layer interface in an inverted polymer solar cell (i-PSC), simply by incorporating an electron-acceptor self-assembled monolayer (SAM)--tetrafluoroterephthalic acid (TFTPA)--on the ZnO cathode surface to create an electron-poor surface of TFTPA on ZnO. The TFTPA molecules on ZnO are anchored on the ZnO surface by reacting its carboxyl groups with hydroxyl groups on the ZnO surface, such that the tetrafluoroterephthalate moieties lay on the surface with plane-on electron-poor benzene rings acting as positive charge centers. Upon coating a layer of fullerenes on top of it, the fullerene molecules can be physically adsorbed by Coulombic interaction and facilitate a promoted electron collection from the bulk. The active layer is composed of the mid bandgap polymer poly(3-hexylthiophene) (P3HT) or low bandgap polymer, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl

  6. Controlled Growth of Well-Defined Conjugated Polymers from the Surfaces of Multiwalled Carbon Nanotubes: Photoresponse Enhancement via Charge Separation.

    Science.gov (United States)

    Hou, Wenpeng; Zhao, Ning-Jiu; Meng, Dongli; Tang, Jing; Zeng, Yi; Wu, Yu; Weng, Yangziwan; Cheng, Chungui; Xu, Xiulai; Li, Yi; Zhang, Jian-Ping; Huang, Yong; Bielawski, Christopher W; Geng, Jianxin

    2016-05-24

    The installation of heterojunctions on the surfaces of carbon nanotubes (CNTs) is an effective method for promoting the charge separation processes needed for CNT-based electronics and optoelectronics applications. Conjugated polymers are proven state-of-the-art candidates for modifying the surfaces of CNTs. However, all previous attempts to incorporate conjugated polymers to CNTs resulted in unordered interfaces. Herein we show that well-defined chains of regioregular poly(3-hexylthiophene) (P3HT) were successfully grown from the surfaces of multiwalled CNTs (MWNTs) using surface-initiated Kumada catalyst-transfer polycondensation. The polymerization was found to proceed in a controlled manner as chains of tunable lengths were prepared through variation of the initial monomer-to-initiator ratio. Moreover, it was determined that large-diameter MWNTs afforded highly ordered P3HT aggregates, which exhibited a markedly bathochromically shifted optical absorption due to a high grafting density induced planarization of the polymer chains. Using ultrafast spectroscopy, the heterojunctions formed between the MWNTs and P3HT were shown to effectively overcome the binding energy of excitons, leading to photoinduced electron transfer from P3HT to MWNTs. Finally, when used as prototype devices, the individual MWNT-g-P3HT core-shell structures exhibited excellent photoresponses under a low illumination density.

  7. Mass and charge transfer on various relevant scales in polymer electrolyte fuel cells[Dissertation 16991

    Energy Technology Data Exchange (ETDEWEB)

    Freunberger, S. A.

    2007-07-01

    This dissertation is concerned with the development, experimental diagnostics and mathematical modelling and simulation of polymer electrolyte fuel cells (PEFC). The central themes throughout this thesis are the closely interlinked phenomena of mass and charge transfer. In the face of developing a PEFC system for vehicle propulsion these phenomena are scrutinized on a broad range of relevant scales. Starting from the material related level of the membrane and the gas diffusion layer (GDL) we turn to length scales, where structural features of the cell additionally come into play. These are the scale of flow channels and ribs, the single cell and the cell stack followed by the cell, stack, and system development for an automotive power train. In Chapter 3 selected fundamental material models and properties, respectively, are explored that are crucial for the mathematical modelling and simulation of PEFC, as needed in some succeeding parts of this work. First, established mathematical models for mass and charge transfer in the membrane are compared within the framework of the membrane electrode assembly (MEA), which represents the electrochemical unit. Second, reliable values for effective diffusivities in the GDLs which are vital for the simulation of gaseous mass transport are measured. Therefore, a method is developed that allows measuring this quantity both as a function of compression and direction as this is a prerequisite of sophisticated more-dimensional numerical PEFC-models. Besides the cross section of the catalyst layer (CL) mass transfer under channels and ribs is considered as a major source of losses in particular under high load operation. As up to now there have been solely non-validated theoretical investigations, in Chapter 4 an experimental method is developed that is for the first time capable of resolving the current density distribution on the this scale. For this, the electron conductors in the cell are considered as 2-dimensional shunt

  8. Hemocompatibility of pseudozwitterionic polymer brushes with a systematic well-defined charge-bias control.

    Science.gov (United States)

    Jhong, Jheng-Fong; Sin, Mei-Chan; Kung, Hsiao-Han; Chinnathambi, Arunachalam; Alharbi, Sulaiman Ali; Chang, Yung

    2014-01-01

    In this study, a pseudozwitterionic surface bearing positively and negatively mixed charged moieties was developed as a potential hemocompatible material for biomedical applications. In this work, hemocompatility of pseudozwitterionic surface prepared from copolymerization of negatively charged 3-sulfopropyl methacrylate (SA) and positively charged [2-(methacryloyloxy)ethyl] trimethylammonium (TMA) was delineated. Mixed charge distribution in the prepared poly(TMA-co-SA)-grafted surface can be controlled by regulating TMA and SA monomer ratios via surface-initiated atom transfer radical polymerization. The effects of grafting composition and charge bias variations on blood compatibility of poly(TMA-co-SA)-grafted surface were reported. The protein adsorption on different poly(TMA-co-SA)-grafted surfaces from human plasma protein (fibrinogen, HSA, and γ-globulin) solutions was evaluated using an enzyme-linked immunosorbent assay. Blood platelet adhesion and time measurements on plasma clotting were conducted to determine the platelet activation on the grafted surface. It was found that the protein resistance and anti-blood cell adhesion of prepared surface can be precisely controlled by controlling the charge balance of TMA/SA compositions. In addition, different charge bias variations on the poly(TMA-co-SA)-grafted surface would induce electrostatic interactions between plasma proteins and prepared surfaces which lead to adsorptions of interfacial protein and blood cells, plasma clotting, and blood cell hemolysis. Results from this study suggest that the hemocompatility of mixed charged poly(TMA-co-SA)-grafted surface depends on the charge bias level. This provides a great potential for designing biomaterial with unique surface chemical structure which could be used in contact with human blood.

  9. Electromechanical characterization of non-uniform charged ionic polymer-metal composites (IPMC) devices

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, B; Branco, P J C [Institute Superior Tecnico, DEEC - Energia, Lisboa 1096-001 (Portugal)], E-mail: pbranco@ist.utl.pt

    2008-08-15

    Research on electromechanical characterization of non-uniformly charged IPMCs is quasi-absent. This has limited their use to only those devices where the IPMC is completely covered with electrode surfaces (uniformly charged). In this paper, we develop a theoretical study for electromechanical characterization of non-uniformly charged IPMCs. A continuum model taking into account the gravitational forces, important for large IPMCs, is presented. Based on this approach, FEM analysis of IPMC devices using Comsol Multiphysics is introduced in a very simple way. Three devices have been studied, comparing the analytical model results with those ones obtained from a FEM analysis.

  10. Space-charge-mediated anomalous ferroelectric switching in P(VDF-TrEE) polymer films

    KAUST Repository

    Hu, Weijin

    2014-11-12

    We report on the switching dynamics of P(VDF-TrEE) copolymer devices and the realization of additional substable ferroelectric states via modulation of the coupling between polarizations and space charges. The space-charge-limited current is revealed to be the dominant leakage mechanism in such organic ferroelectric devices, and electrostatic interactions due to space charges lead to the emergence of anomalous ferroelectric loops. The reliable control of ferroelectric switching in P(VDF-TrEE) copolymers opens doors toward engineering advanced organic memories with tailored switching characteristics.

  11. Development of Efficient Charge-Selective Materials for Bulk Heterojunction Polymer Solar Cells

    Science.gov (United States)

    2015-01-15

    high-efficiency PSCs and PVSCs. 15. SUBJECT TERMS Nanocomposites, Polymer Composites, Organic Photovoltaic Cells, Polymer Solar Cells 16...activation process. FPI can also serve as a dopant to dope PC61BM to achieve high conductivity (3.2 x 10-2 S/cm) in thin film as well. Thereby, the...Perovskite Thin Films ” ACS Nano 2014, 8, 10640-10654. 11. L. J. Zuo, C. C. Chueh, Y. X. Xu, K. S. Chen, Y. Zang, C. Z. Li, H. Z. Chen, A. K.-Y. Jen

  12. Charge carrier motion in disordered conjugated polymers: a multiscale ab-initio study

    Energy Technology Data Exchange (ETDEWEB)

    Vukmirovic, Nenad; Wang, Lin-Wang

    2009-11-10

    We developed an ab-initio multiscale method for simulation of carrier transport in large disordered systems, based on direct calculation of electronic states and electron-phonon coupling constants. It enabled us to obtain the never seen before rich microscopic details of carrier motion in conjugated polymers, which led us to question several assumptions of phenomenological models, widely used in such systems. The macroscopic mobility of disordered poly(3- hexylthiophene) (P3HT) polymer, extracted from our simulation, is in agreement with experimental results from the literature.

  13. Lattice cluster theory of associating polymers. II. Enthalpy and entropy of self-assembly and Flory-Huggins interaction parameter χ for solutions of telechelic molecules.

    Science.gov (United States)

    Dudowicz, Jacek; Freed, Karl F; Douglas, Jack F

    2012-02-14

    The lattice cluster theory for solutions of telechelic polymer chains, developed in paper I, is applied to determine the enthalpy Δh(p) and entropy Δs(p) of self-assembly of linear telechelics and to evaluate the Flory-Huggins (FH) interaction parameter χ governing the phase behavior of these systems. Particular focus is placed on examining how these interaction variables depend on the composition of the solution, temperature, van der Waals and local "sticky" interaction energies, and the length of the individual telechelic chains. The FH interaction parameter χ is found to exhibit an entropy-enthalpy compensation effect between the "entropic" and "enthalpic" portions as either the composition or mass of the telechelic species is varied, providing unique theoretical insights into this commonly reported, yet, enigmatic phenomenon.

  14. Dopant-induced crossover from 1D to 3D charge transport in conjugated polymers

    OpenAIRE

    Reedijk, JA; Martens, HCF; Brom, HB Hans; Michels, MAJ Thijs

    1999-01-01

    The interplay between inter- and intra-chain charge transport in bulk polythiophene in the hopping regime has been clarified by studying the conductivity as a function of frequency (up to 3 THz), temperature and doping level. We present a model which quantitatively explains the observed crossover from quasi-one-dimensional transport to three-dimensional hopping conduction with increasing doping level. At high frequencies the conductivity is dominated by charge transport on one-dimensional con...

  15. 2D Coherent Charge Transport in Highly Ordered Conducting Polymers Doped by Solid State Diffusion

    OpenAIRE

    Kang, Keehoon; Watanabe, Shun; Broch, Katharina; Sepe, Alessandro; Brown, Adam; Nasrallah, Iyad; Nikolka, Mark; Fei, Zhuping; Heeney, Martin; Matsumoto, Daisuke; Marumoto, Kazuhiro; Tanaka, Hisaaki; Kuroda, Shin-ichi; Sirringhaus, Henning

    2016-01-01

    This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by the Nature Publishing Group. Doping is one of the most important methods to control charge carrier concentration in semiconductors. Ideally, the introduction of dopants should not perturb the ordered microstructure of the semiconducting host. In some systems, such as modulation-doped inorganic semiconductors or molecular charge transfer crystals, this can be achieved by spatially sepa...

  16. Surfactant mediated self-assembly of weakly charged polymer on hydrophobic polymeric substrate

    Science.gov (United States)

    Goswami, Monojoy; Sumpter, Bobby

    2011-03-01

    Molecular Dynamics (MD) simulations are carried out to understand the physical aspects of different bulk morphologies formed in charged diblock copolymers. It has been seen that the bulk morphologies formed by charged block copolymers, 75 vol % fluorinated polyisoprene (FPI) - 25 vol% sulfonated polystyrene (PSS) with 50% sulfonation are substantially different from their diblock counterparts. In this study we show how the bulk morphologies change from the uncharged diblock counterparts and also how morphology can be tuned with volume fraction of the charged block and with a change in dielectric constant. A physical understanding based on the underlying strong electrostatic interactions between the charged block and counterions is obtained. The 75/25 diblock shows hexagonal morphologies with the minority blocks (PSS) forming the continuous phase due to charge percolation and the FPI blocks arranged in hexagonal cylinders. Some long-range order can be sustained even by changing the dielectric of the medium. Diverse and atypical morphologies are readily accessible by simply changing the number distribution of the charges on PSS block.

  17. Role of Balanced Charge Carrier Transport in Low Band Gap polymer : fullerene Bulk Heterojunction Solar Cells

    NARCIS (Netherlands)

    Kotlarski, Jan D.; Moet, Date J. D.; Blom, Paul W. M.

    2011-01-01

    Lowering of the optical band gap of conjugated polymers in bulk heterojunction solar cells not only leads to an increased absorption but also to an increase of the optimal active layer thickness due to interference effects at longer wavelengths. The increased carrier densities due to the enhanced ab

  18. Synthesis and Charge Transport Properties of Polymers Derived from Oxidation of 1-H-1’(6-pyrrol-1-yl)-hexyl-4,4’-bipyridinium

    Science.gov (United States)

    1988-08-15

    platinized poly(3- methylthiophene),7b a viologen /quinone polymer, 9 ferrocyanide-loaded protonated poly(4-vinylpyridine),l 0 and electroactive metal oxides...article describes the synthesis and electrochemical properties of redox polymers, having a poly- pyrrole backbone and viologen subunits, derived from...study aspects of the charge transport behavior of the viologen redox system. Poly(P-V-Me2 ) and poly(P-V-H2+ ) have been used to investigate the

  19. 35Cl NQR study of lattice dynamic and magnetic property of a crystalline coordination polymer {CuCA(phz)(H 2O) 2} n

    Science.gov (United States)

    Gotoh, Kazuma; Terao, Takeshi; Asaji, Tetsuo

    2007-01-01

    Copper(II) compounds {CuCA(phz)(H 2O) 2} n (H 2CA = chloranilic acid, phz = phenazine) having a layer structure of -CuCA(H 2O) 2- polymer chains and phenazine were studied by 35Cl nuclear quadrupole resonance (NQR). The single NQR line observed at 35.635 MHz at 261.5 K increased to 35.918 MHz at 4.2 K. The degree of reduction of electric field gradient due to lattice vibrations was similar to that of chloranilic acid crystal. Temperature dependence of spin-lattice relaxation time, T1, of the 35Cl NQR signal below 20 K, between 20 and 210 K, and above 210 K, was explained by (1) a decrease of effective electron-spin density caused by antiferromagnetic interaction, (2) a magnetic interaction between Cl nuclear-spin and electron-spins on paramagnetic Cu(II) ions, and (3) an increasing contribution from reorientation of ligand molecules, respectively. The electron spin-exchange parameter ∣ J∣ between the neighboring Cu(II) electrons was estimated to be 0.33 cm -1 from the T1 value of the range 20-210 K. Comparing this value with that of J = -1.84 cm -1 estimated from the magnetic susceptibility, it is suggested that the magnetic dipolar coupling with the electron spins on Cu(II) ions must be the principal mechanism for the 35Cl NQR spin-lattice relaxation of {CuCA(phz)(H 2O) 2} n but a delocalization of electron spin over the chloranilate ligand has to be taken into account.

  20. PHOTOREFRACTIVE POLYMERS

    NARCIS (Netherlands)

    Morichere, D; Malliaras, G.G; Krasnikov, V.V.; Bolink, H.J; Hadziioannou, G

    1995-01-01

    The use of polymers as photorefractive materials offers many advantages : flexibility in synthesis, doping, processing and low cost. The required functionalities responsible for photorefractivity, namely charge generation, transport, trapping and linear electrooptic effect are given in the polymer w

  1. PHOTOREFRACTIVE POLYMERS

    NARCIS (Netherlands)

    Morichere, D; Malliaras, G.G; Krasnikov, V.V.; Bolink, H.J; Hadziioannou, G

    1995-01-01

    The use of polymers as photorefractive materials offers many advantages : flexibility in synthesis, doping, processing and low cost. The required functionalities responsible for photorefractivity, namely charge generation, transport, trapping and linear electrooptic effect are given in the polymer w

  2. Charge carrier photogeneration in conjugated polymer PhPPV/R6G composite system

    Institute of Scientific and Technical Information of China (English)

    WANG Huan; TIAN Wenjing

    2005-01-01

    The spectral and polarity dependence of the quantum yield of charge carrier photo-generation was studied by steady-state photocurrent measurement in a single layer PhPPV film, double layer film of PhPPV and R6G and doped film of PhPPV with R6G. The intrinsic and extrinsic charge carrier photogeneration was observed. The result indicates that the quantum efficiency of the double layer device is higher than that of single layer device under reverse bias, but it is opposite under forward bias. The yield of charge carrier photogeneration of the doped film is higher than that of the other two films at both forward and reverse bias because of the increased interface area between the electron donor and acceptor.

  3. Structural origin of gap states in semicrystalline polymers and the implications for charge transport

    KAUST Repository

    Rivnay, Jonathan

    2011-03-16

    We quantify the degree of paracrystalline disorder in the π-π stacking direction of crystallites of a high performing semicrystalline semiconducting polymer with advanced x-ray line-shape analysis. Using density functional theory calculations to provide input to a simple tight-binding model, we obtain the density of states of a system of π-π stacked polymer chains with increasing amounts of paracrystalline disorder. We find that, for an aligned film of PBTTT, the paracrystalline disorder is 7.3%. This type of disorder induces a tail of trap states with a breadth of ∼100 meV as determined through calculation. This finding agrees with previous device modeling and provides physical justification for the mobility edge model. © 2011 American Physical Society.

  4. Photoinduced charge and energy transfer in dye-doped conjugated polymers

    NARCIS (Netherlands)

    Veldman, D.; Bastiaansen, J.J.A.M.; Langeveld-Voss, B.M.W.; Sweelssen, J.; Koetse, M.M.; Meskers, S.C.J.; Janssen, R.A.J.

    2006-01-01

    Conjugated polymer-molecular dye blends of MDMO-PPV (poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene]) and PF1CVTP (poly[9,9-dioctylfluorene-2,7-diyl-alt-2,5-bis(2-thienyl-1-cyanovinyl)-1-(3′,7′-dimethyloctyloxy)-4-methoxybenzene-5″,5″-diyl]) with three dipyrrometheneboron difluoride

  5. Unified description of charge-carrier mobilities in disordered semiconducting polymers

    NARCIS (Netherlands)

    Pasveer, WF; Cottaar, J; Tanase, C; Coehoorn, R; Bobbert, PA; Blom, PWM; de Leeuw, DM; Michels, MAJ

    2005-01-01

    From a numerical solution of the master equation for hopping transport in a disordered energy landscape with a Gaussian density of states, we determine the dependence of the charge-carrier mobility on temperature, carrier density, and electric field. Experimental current-voltage characteristics in d

  6. Surface charge-specific interactions between polymer nanoparticles and ABC transporters in Caco-2 cells

    NARCIS (Netherlands)

    Bhattacharjee, S.; Opstal, van E.J.; Alink, G.M.; Marcelis, A.T.M.; Zuilhof, H.; Rietjens, I.M.C.M.

    2013-01-01

    The surface charge-dependent transport of polymeric nanoparticles (PNPs) across Caco-2 monolayers grown on transwell culture systems as an in vitro model for intestinal transport was tested. The transport of well-characterized, monodisperse, and fluorescent tri-block copolymer nanoparticles (TCNPs/s

  7. A theoretical method to compute sequence dependent configurational properties in charged polymers and proteins

    Energy Technology Data Exchange (ETDEWEB)

    Sawle, Lucas; Ghosh, Kingshuk, E-mail: kghosh@du.edu [Department of Physics and Astronomy, University of Denver, Denver, Colorado 80208 (United States)

    2015-08-28

    A general formalism to compute configurational properties of proteins and other heteropolymers with an arbitrary sequence of charges and non-uniform excluded volume interaction is presented. A variational approach is utilized to predict average distance between any two monomers in the chain. The presented analytical model, for the first time, explicitly incorporates the role of sequence charge distribution to determine relative sizes between two sequences that vary not only in total charge composition but also in charge decoration (even when charge composition is fixed). Furthermore, the formalism is general enough to allow variation in excluded volume interactions between two monomers. Model predictions are benchmarked against the all-atom Monte Carlo studies of Das and Pappu [Proc. Natl. Acad. Sci. U. S. A. 110, 13392 (2013)] for 30 different synthetic sequences of polyampholytes. These sequences possess an equal number of glutamic acid (E) and lysine (K) residues but differ in the patterning within the sequence. Without any fit parameter, the model captures the strong sequence dependence of the simulated values of the radius of gyration with a correlation coefficient of R{sup 2} = 0.9. The model is then applied to real proteins to compare the unfolded state dimensions of 540 orthologous pairs of thermophilic and mesophilic proteins. The excluded volume parameters are assumed similar under denatured conditions, and only electrostatic effects encoded in the sequence are accounted for. With these assumptions, thermophilic proteins are found—with high statistical significance—to have more compact disordered ensemble compared to their mesophilic counterparts. The method presented here, due to its analytical nature, is capable of making such high throughput analysis of multiple proteins and will have broad applications in proteomic studies as well as in other heteropolymeric systems.

  8. Optimized Wang-Landau sampling of lattice polymers: ground state search and folding thermodynamics of HP model proteins.

    Science.gov (United States)

    Wüst, Thomas; Landau, David P

    2012-08-14

    Coarse-grained (lattice-) models have a long tradition in aiding efforts to decipher the physical or biological complexity of proteins. Despite the simplicity of these models, however, numerical simulations are often computationally very demanding and the quest for efficient algorithms is as old as the models themselves. Expanding on our previous work [T. Wüst and D. P. Landau, Phys. Rev. Lett. 102, 178101 (2009)], we present a complete picture of a Monte Carlo method based on Wang-Landau sampling in combination with efficient trial moves (pull, bond-rebridging, and pivot moves) which is particularly suited to the study of models such as the hydrophobic-polar (HP) lattice model of protein folding. With this generic and fully blind Monte Carlo procedure, all currently known putative ground states for the most difficult benchmark HP sequences could be found. For most sequences we could also determine the entire energy density of states and, together with suitably designed structural observables, explore the thermodynamics and intricate folding behavior in the virtually inaccessible low-temperature regime. We analyze the differences between random and protein-like heteropolymers for sequence lengths up to 500 residues. Our approach is powerful both in terms of robustness and speed, yet flexible and simple enough for the study of many related problems in protein folding.

  9. Optimized Wang-Landau sampling of lattice polymers: Ground state search and folding thermodynamics of HP model proteins

    Science.gov (United States)

    Wüst, Thomas; Landau, David P.

    2012-08-01

    Coarse-grained (lattice-) models have a long tradition in aiding efforts to decipher the physical or biological complexity of proteins. Despite the simplicity of these models, however, numerical simulations are often computationally very demanding and the quest for efficient algorithms is as old as the models themselves. Expanding on our previous work [T. Wüst and D. P. Landau, Phys. Rev. Lett. 102, 178101 (2009)], 10.1103/PhysRevLett.102.178101, we present a complete picture of a Monte Carlo method based on Wang-Landau sampling in combination with efficient trial moves (pull, bond-rebridging, and pivot moves) which is particularly suited to the study of models such as the hydrophobic-polar (HP) lattice model of protein folding. With this generic and fully blind Monte Carlo procedure, all currently known putative ground states for the most difficult benchmark HP sequences could be found. For most sequences we could also determine the entire energy density of states and, together with suitably designed structural observables, explore the thermodynamics and intricate folding behavior in the virtually inaccessible low-temperature regime. We analyze the differences between random and protein-like heteropolymers for sequence lengths up to 500 residues. Our approach is powerful both in terms of robustness and speed, yet flexible and simple enough for the study of many related problems in protein folding.

  10. Concentration and mobility of charge carriers in thin polymers at high temperature determined by electrode polarization modeling

    Science.gov (United States)

    Diaham, Sombel; Locatelli, Marie-Laure

    2012-07-01

    Charge carrier concentration (n0) and effective mobility (μeff) are reported in two polymer films (dielectric spectroscopy data. It is shown that the glass transition temperature (Tg) occurrence has a strong influence on the temperature dependence of n0 and μeff. We carry out that n0 presents two distinct Arrhenius-like behaviors below and above Tg, while μeff exhibits a Vogel-Fulcher-Tamman behavior only above Tg whatever the polymer under study. For polyimide films, n0 varies from 1 × 1014 to 4 × 1016 cm-3 and μeff from 1 × 10-8 to 2 × 10-6 cm2 V-1 s-1 between 200 °C to 400 °C. Poly(amide-imide) films show n0 values between 6 × 1016 and 4 × 1018 cm-3 from 270 °C to 400 °C, while μeff varies between 1 × 10-10 and 2 × 10-7 cm2 V-1 s-1. Considering the activation energies of these physical parameters in the temperature range of investigation, n0 and μeff values appear as coherent with those reported in the literature at lower temperature (Polyimide films appear as good candidates due to nS values less than 1011 cm-2 up to 300 °C.

  11. Spontaneously formed high-performance charge-transport layers of organic single-crystal semiconductors on precisely synthesized insulating polymers

    Science.gov (United States)

    Makita, Tatsuyuki; Sasaki, Masayuki; Annaka, Tatsuro; Sasaki, Mari; Matsui, Hiroyuki; Mitsui, Chikahiko; Kumagai, Shohei; Watanabe, Shun; Hayakawa, Teruaki; Okamoto, Toshihiro; Takeya, Jun

    2017-04-01

    Charge-transporting semiconductor layers with high carrier mobility and low trap-density, desired for high-performance organic transistors, are spontaneously formed as a result of thermodynamic phase separation from a blend of π-conjugated small molecules and precisely synthesized insulating polymers dissolved in an aromatic solvent. A crystal film grows continuously to the size of centimeters, with the critical conditions of temperature, concentrations, and atmosphere. It turns out that the molecular weight of the insulating polymers plays an essential role in stable film growth and interfacial homogeneity at the phase separation boundary. Fabricating the transistor devices directly at the semiconductor-insulator boundaries, we demonstrate that the mixture of 3,11-didecyldinaphtho[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene and poly(methyl methacrylate) with the optimized weight-average molecular weight shows excellent device performances. The spontaneous phase separation with a one-step fabrication process leads to a high mobility up to 10 cm2 V-1 s-1 and a low subthreshold swing of 0.25 V dec-1 even without any surface treatment such as self-assembled monolayer modifications on oxide gate insulators.

  12. Adsorption of the Inflammatory Mediator High-Mobility Group Box 1 by Polymers with Different Charge and Porosity

    Directory of Open Access Journals (Sweden)

    Carla Tripisciano

    2014-01-01

    Full Text Available High-mobility group box 1 protein (HMGB1 is a conserved protein with a variety of biological functions inside as well as outside the cell. When released by activated immune cells, it acts as a proinflammatory cytokine. Its delayed release has sparked the interest in HMGB1 as a potential therapeutic target. Here, we studied the adsorption of HMGB1 to anionic methacrylate-based polymers as well as to neutral polystyrene-divinylbenzene copolymers. Both groups of adsorbents exhibited efficient binding of recombinant HMGB1 and of HMGB1 derived from lipopolysaccharide-stimulated peripheral blood mononuclear cells. The adsorption characteristics depended on particle size, porosity, accessibility of the pores, and charge of the polymers. In addition to these physicochemical parameters of the adsorbents, modifications of the molecule itself (e.g., acetylation, phosphorylation, and oxidation, interaction with other plasma proteins or anticoagulants (e.g., heparin, or association with extracellular microvesicles may influence the binding of HMGB1 to adsorbents and lead to preferential depletion of HMGB1 subsets with different biological activity.

  13. Laser-induced forward transfer of polymer light-emitting diode pixels with increased charge injection.

    Science.gov (United States)

    Shaw-Stewart, James; Lippert, Thomas; Nagel, Matthias; Nüesch, Frank; Wokaun, Alexander

    2011-02-01

    Laser-induced forward transfer (LIFT) has been used to print 0.6 mm × 0.5 mm polymer light-emitting diode (PLED) pixels with poly[2-methoxy, 5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) as the light-emitting polymer. The donor substrate used in the LIFT process is covered by a sacrificial triazene polymer (TP) release layer on top of which the aluminium cathode and functional MEH-PPV layers are deposited. To enhance electron injection into the MEH-PPV layer, a thin poly(ethylene oxide) (PEO) layer on the Al cathode or a blend of MEH-PPV and PEO was used. These donor substrates have been transferred onto both plain indium tin oxide (ITO) and bilayer ITO/PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) blend) receiver substrates to create the PLED pixels. For comparison, devices were fabricated in a conventional manner on ITO substrates coated with a PEDOT:PSS hole-transporting layer. Compared to multilayer devices without PEO, devices with ITO/PEDOT:PSS/MEH-PPV:PEO blend/Al architecture show a 100 fold increase of luminous efficiency (LE) reaching a maximum of 0.45 cd/A for the blend at a brightness of 400 cd/m(2). A similar increase is obtained for the polymer light-emitting diode (PLED) pixels deposited by the LIFT process, although the maximum luminous efficiency only reaches 0.05 cd/A for MEH-PPV:PEO blend, which we have attributed to the fact that LIFT transfer was carried out in an ambient atmosphere. For all devices, we confirm a strong increase in device performance and stability when using a PEDOT:PSS film on the ITO anode. For PLEDs produced by LIFT, we show that a 25 nm thick PEDOT:PSS layer on the ITO receiver substrate considerably reduces the laser fluence required for pixel transfer from 250 mJ/cm(2) without the layer to only 80 mJ/cm(2) with the layer.

  14. Charge Transfer Complexes of Polymers%高分子电荷转移复合物

    Institute of Scientific and Technical Information of China (English)

    赵扬; 邱家白

    1986-01-01

    @@ 电荷转移复合物(charge transfer complex, CTC)的研究,始于本世纪二十年代。然而对CTC理论的阐述,及其实际应用方面,长期未取得实质性进展。1952年R. S. Mulliken在J. H. Hildebrand的实验基础上首创共振模型,引入电荷转移(charge transfer,CT)这一术语,奠定了CTO的理论基础。从此,对CT现象的研究不断深入,开拓的领域日益广阔,已成为世界性的研究课题。

  15. Pressure dependence of space charge deposition in piezoelectric polymer foams: simulations and experimental verification

    Science.gov (United States)

    Harris, Scott; Mellinger, Axel

    2012-06-01

    The piezoelectric activity of PQ-50 cellular polypropylene (PP) foam (an example of a so-called ferroelectret) is measured after repeated charging in a nitrogen atmosphere at a range of pressures between 61 and 381 kPa. The results are compared against simulations using a multilayer electromechanical model based on Townsend's model of Paschen breakdown and a realistic distribution of void heights determined from scanning electron micrographs. The modeled piezoelectric coefficients versus pressure are in good agreement with experimental data when adjusted Paschen coefficients are used, indicating that the Paschen curve for electric breakdown in gases needs to be modified for dielectric barrier discharges in microcavities. The highest d 33 coefficients were achieved for pressures above 251 kPa. For previously uncharged PP foam, the model predicts an optimal charging pressure of 186 kPa.

  16. Surface charge-specific interactions between polymer nanoparticles and ABC transporters in Caco-2 cells

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Sourav, E-mail: sourav.bhattacharjee@wur.nl [Wageningen University, Laboratory of Organic Chemistry (Netherlands); Opstal, Edward J. van; Alink, Gerrit M. [Wageningen University, Division of Toxicology (Netherlands); Marcelis, Antonius T. M.; Zuilhof, Han [Wageningen University, Laboratory of Organic Chemistry (Netherlands); Rietjens, Ivonne M. C. M. [Wageningen University, Division of Toxicology (Netherlands)

    2013-06-15

    The surface charge-dependent transport of polymeric nanoparticles (PNPs) across Caco-2 monolayers grown on transwell culture systems as an in vitro model for intestinal transport was tested. The transport of well-characterized, monodisperse, and fluorescent tri-block copolymer nanoparticles (TCNPs/size {approx}45 nm) and polystyrene nanoparticles (PSNPs/size {approx}50 nm), with different surface charges (positive and negative), was quantified. The positive PNPs showed a higher intracellular uptake and flux across the Caco-2 monolayers than the negative PNPs. Multidrug resistance/P-glycoprotein (MDR1/P-gp), a specific ATP-binding cassette (ABC) transporter, was found to play a major role in the cellular efflux of positive PNPs, whereas the multidrug resistance protein 1 took part in the efflux of negative PNPs from Caco-2 cells. The positive PNPs also caused an increased cellular uptake and apical to basolateral transport of the carcinogen PhIP across the Caco-2 monolayer. The flavonoid quercetin, which is known to interact with ABC transporters, promoted the intracellular uptake of different PNPs and interfered with the normal distribution patterns of PNPs in the transwell system. These results indicate that PNPs display surface charge-specific interactions with ABC transporters and can even affect the bioavailability of toxic food-borne compounds (like pro-carcinogens).

  17. Charged Metalloporphyrin Polymers for Cooperative Synthesis of Cyclic Carbonates from CO2 under Ambient Conditions.

    Science.gov (United States)

    Chen, Yaju; Luo, Rongchang; Xu, Qihang; Jiang, Jun; Zhou, Xiantai; Ji, Hongbing

    2017-06-09

    A facile and one-pot synthesis of metalloporphyrin-based ionic porous organic polymers (M-iPOPs) was performed through a typical Yamamoto-Ullmann coupling reaction for the first time. We used various characterization techniques to demonstrate that these strongly polar Al-based materials (Al-iPOP) possessed a relatively uniform microporosity, good swellable features, and a good CO2 capture capacity. If we consider the particular physicochemical properties, heterogeneous Al-iPOP, which bears both a metal active center and halogen anion, acted as a bifunctional catalyst for the solvent- and additive-free synthesis of cyclic carbonates from various epoxides and CO2 with an excellent activity and good recyclability under mild conditions. Interestingly, these CO2 -philic materials could catalyze the cycloaddition reaction smoothly by using simulated flue gas (15 % CO2 in N2 , v/v) as a raw material, which indicates that a stable local microenvironment and polymer swellability might promote the transformation. Thus, the introduction of polar ionic liquid units into metalloporphyrin-based porous materials is regarded as a promising new strategy for the chemical conversion of CO2 . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Formation of polaron pairs and time-resolved photogeneration of free charge carriers in π-conjugated polymers

    Science.gov (United States)

    Frankevich, Eugene; Ishii, Hisao; Hamanaka, Yasushi; Yokoyama, Takahiro; Fuji, Akihiko; Li, Sergey; Yoshino, Katsumi; Nakamura, Arao; Seki, Kazuhiko

    2000-07-01

    We have performed in the present work time-resolved experiments on poly(3-dodecyl-thiophene) (P3DDT) and poly(2,5-dioctyloxy-p-phenylene vinylene) (OO-PPV) films by directly probing the formation of charge carriers responsible for the cw photoconductivity within the time domain of -10 ps to 1 ns. Laser light pulses of 400 nm wavelength, 150 fs width, induced photoconductivity in a sample with a frequency 1 kHz. Red 800 nm light pulses delayed in respect to blue ones were revealed to affect the photoconductivity. The effect of the second pulses increased with the delay time. Red light induced changes of the photoconductivity were positive in OO-PPV, and negative in P3DDT. These results are rationalized as an evidence of delayed not immediate formation of free charge carriers. The carriers seem to be formed within 10 ps after the pumping pulse. A mechanism of formation of free polarons from polaron pair is suggested, which has permitted to explain main feature of the results including different signs of the effect of the red light in different polymers.

  19. Investigation of charge injection and transport behavior in multilayer structure consisted of ferromagnetic metal and organic polymer under external fields

    Science.gov (United States)

    Zhao, Hua; Meng, Wei-Feng

    2017-10-01

    In this paper a five layer organic electronic device with alternately placed ferromagnetic metals and organic polymers: ferromagnetic metal/organic layer/ferromagnetic metal/organic layer/ferromagnetic metal, which is injected a spin-polarized electron from outsides, is studied theoretically using one-dimensional tight binding model Hamiltonian. We calculated equilibrium state behavior after an electron with spin is injected into the organic layer of this structure, charge density distribution and spin polarization density distribution of this injected spin-polarized electron, and mainly studied possible transport behavior of the injected spin polarized electron in this multilayer structure under different external electric fields. We analyze the physical process of the injected electron in this multilayer system. It is found by our calculation that the injected spin polarized electron exists as an electron-polaron state with spin polarization in the organic layer and it can pass through the middle ferromagnetic layer from the right-hand organic layer to the left-hand organic layer by the action of increasing external electric fields, which indicates that this structure may be used as a possible spin-polarized charge electronic device and also may provide a theoretical base for the organic electronic devices and it is also found that in the boundaries between the ferromagnetic layer and the organic layer there exist induced interface local dipoles due to the external electric fields.

  20. Dynamics of Photogenerated Polarons in Conjugated Polymers

    Science.gov (United States)

    An, Z.; Wu, C. Q.; Sun, X.

    2004-11-01

    Within a tight-binding electron-phonon interacting model, we investigate the dynamics of photoexcitations to address the generation mechanism of charged polarons in conjugated polymers by using a nonadiabatic evolution method. Besides the neutral polaron exciton which is well known, we identify a novel product of lattice dynamic relaxation from the photoexcited states in a few hundreds of femtoseconds, which is a mixed state composed of both charged polarons and neutral excitons. Our results show that the charged polarons are generated directly with a yield of about 25%, which is independent of the excitation energies, in good agreement with results from experiments. Effects of the conjugation length are also discussed.

  1. Functionalized 2D-MoS2-Incorporated Polymer Ternary Solar Cells: Role of Nanosheet-Induced Long-Range Ordering of Polymer Chains on Charge Transport.

    Science.gov (United States)

    Ahmad, Razi; Srivastava, Ritu; Yadav, Sushma; Chand, Suresh; Sapra, Sameer

    2017-09-19

    In this paper, we demonstrated the enhancement in power conversion efficiency (PCE) of solar cells based on poly(3-hexylthiophene-2,5-diyl) (P3HT)/[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) by incorporation of functionalized 2D-MoS2 nanosheets (NSs) as an additional charge-transporting material. The enhancement in PCE of ternary solar cells arises due to the synergic enhancement in exciton dissociation and the improvement in mobility of both electrons and holes through the active layer of the solar cells. The improved hole mobility is attributed to the formation of the long-range ordered nanofibrillar structure of polymer phases and improved crystallinity in the presence of 2D-MoS2 NSs. The improved electron mobility arises due to the highly conducting 2D network of MoS2 NSs which provides additional electron transport channels within the active layer. The nanosheet-incorporated ternary blend solar cells exhibit 32% enhancement in PCE relative to the binary blend P3HT/PC71BM.

  2. Thiophene fused azacoronenes: regioselective synthesis, self organization, charge transport, and its incorporation in conjugated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi; He, Bo

    2015-09-15

    A regioselective synthesis of an azacoronene fused with two peripheral thiophene groups has been realized through a concise synthetic route. The resulting thienoazacoronene (TAC) derivatives show high degree of self-organization in solution, in single crystals, in the bulk, and in spuncast thin films. Spuncast thin film field-effect transistors of the TACs exhibited mobilities up to 0.028 cm.sup.2V.sup.-1 S.sup.-1, which is among the top field effect mobilities for solution processed discotic materials. Organic photovoltaic devices using TAC-containing conjugated polymers as the donor material exhibited a high open-circuit voltage of 0.89 V, which was ascribable to TAC's low-lying highest occupied molecular orbital energy level.

  3. Thiophene fused azacoronenes: regioselective synthesis, self organization, charge transport, and its incorporation in conjugated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi; He, Bo

    2015-09-15

    A regioselective synthesis of an azacoronene fused with two peripheral thiophene groups has been realized through a concise synthetic route. The resulting thienoazacoronene (TAC) derivatives show high degree of self-organization in solution, in single crystals, in the bulk, and in spuncast thin films. Spuncast thin film field-effect transistors of the TACs exhibited mobilities up to 0.028 cm.sup.2V.sup.-1 S.sup.-1, which is among the top field effect mobilities for solution processed discotic materials. Organic photovoltaic devices using TAC-containing conjugated polymers as the donor material exhibited a high open-circuit voltage of 0.89 V, which was ascribable to TAC's low-lying highest occupied molecular orbital energy level.

  4. Modeling of mass and charge transport in a solid oxide fuel cell anode structure by a 3D lattice Boltzmann approach

    Science.gov (United States)

    Paradis, Hedvig; Andersson, Martin; Sundén, Bengt

    2016-08-01

    A 3D model at microscale by the lattice Boltzmann method (LBM) is proposed for part of an anode of a solid oxide fuel cell (SOFC) to analyze the interaction between the transport and reaction processes and structural parameters. The equations of charge, momentum, heat and mass transport are simulated in the model. The modeling geometry is created with randomly placed spheres to resemble the part of the anode structure close to the electrolyte. The electrochemical reaction processes are captured at specific sites where spheres representing Ni and YSZ materials are present with void space. This work focuses on analyzing the effect of structural parameters such as porosity, and percentage of active reaction sites on the ionic current density and concentration of H2 using LBM. It is shown that LBM can be used to simulate an SOFC anode at microscale and evaluate the effect of structural parameters on the transport processes to improve the performance of the SOFC anode. It was found that increasing the porosity from 30 to 50 % decreased the ionic current density due to a reduction in the number of reaction sites. Also the consumption of H2 decreased with increasing porosity. When the percentage of active reaction sites was increased while the porosity was kept constant, the ionic current density increased. However, the H2 concentration was slightly reduced when the percentage of active reaction sites was increased. The gas flow tortuosity decreased with increasing porosity.

  5. Spatial profile of charge storage in organic field-effect transistor nonvolatile memory using polymer electret

    Science.gov (United States)

    She, Xiao-Jian; Liu, Jie; Zhang, Jing-Yu; Gao, Xu; Wang, Sui-Dong

    2013-09-01

    Spatial profile of the charge storage in the pentacene-based field-effect transistor nonvolatile memories using poly(2-vinyl naphthalene) electret is probed. The electron trapping into the electret after programming can be space dependent with more electron storage in the region closer to the contacts, and reducing the channel length is an effective approach to improve the memory performance. The deficient electron supply in pentacene is proposed to be responsible for the inhomogeneous electron storage in the electret. The hole trapping into the electret after erasing is spatially homogeneous, arising from the sufficient hole accumulation in the pentacene channel.

  6. Iterative Deconvolution of PEA Measurements for Enhancing the Spatial Resolution of Charge Profile in Space Polymers

    Directory of Open Access Journals (Sweden)

    Mohamad Arnaout

    2016-01-01

    Full Text Available This work aims to improve the PEA calibration technique through defining a well-conditioned transfer matrix. To this end, a numerical electroacoustic model that allows determining the output voltage of the piezoelectric sensor and the acoustic pressure is developed with the software COMSOL®. The proposed method recovers the charge distribution within the sample using an iterative deconvolution method that uses the transfer matrix obtained with the new calibration technique. The obtained results on theoretical and experimental signals show an improvement in the spatial resolution compared with the standard method usually used.

  7. Characterization of the charge transport and electrical properties in solution-processed semiconducting polymers

    Institute of Scientific and Technical Information of China (English)

    WANG LiGuo; ZHANG HuaiWu; TANG XiaoLi; LI YuanXun; ZHONG ZhiYong

    2012-01-01

    The conventional charge transport models based on density- and field-dependent mobility,only having a non-Arrhenius temperature dependence,cannot give good current-voltage characteristics of poly (2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) hole-only devices.In this paper,we demonstrate that the current-voltage characteristics can give a good unified description of the temperature,carrier density and electric field dependence of mobility based on both the Arrhenius temperature dependence and the non-Arrhenius temperature dependence.Furthermore,we perform a systematic study of charge transport and electrical properties for MEH-PPV.It is shown that the boundary carrier density has an important effect on the current-voltage characteristics.Too large or too small values of boundary carder density will lead to incorrect current-voltage characteristics.The numerically calculated carrier density is a decreasing function of the distance to the interface,and the numerically calculated electric field is an increasing function of the distance.Both the maximum of carrier density and the minimum of electric field appear near the interface.

  8. Charge storage in polymer acid-doped polyaniline-based layer-by-layer electrodes.

    Science.gov (United States)

    Jeon, Ju-Won; O'Neal, Josh; Shao, Lin; Lutkenhaus, Jodie L

    2013-10-23

    Polymeric electrodes that can achieve high doping levels and store charge reversibly are desired for electrochemical energy storage because they can potentially achieve high specific capacities and energies. One such candidate is the polyaniline:poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PANI:PAAMPSA) complex, a water-processable complex obtained via template polymerization that is known to reversibly achieve high doping levels at potentials of up to 4.5 V versus Li/Li+. Here, for the first time, PANI:PAAMPSA is successfully incorporated into layer-by-layer (LbL) electrodes. This processing technique is chosen for its ability to blend species on a molecular level and its ability to conformally coat a substrate. Three different polyaniline-based LbL electrodes comprised of PANI/PAAMPSA, PANI/PANI:PAAMPSA, and linear poly(ethylenimine)/PANI:PAAMPSA are compared in terms of film growth, charge storage, and reversibility. We found that the reversibility of PANI:PAAMPSA is retained within the LbL electrodes and that the PANI/PANI:PAAMPSA electrode exhibits the best performance in terms of capacity and cycle life. These results provide general guidelines for the assembly of PANI:PAAMPSA in LbL films and also demonstrate their potential as electrochemically active components in electrodes.

  9. Ultrafast Charge and Triplet State Formation in Diketopyrrolopyrrole Low Band Gap Polymer/Fullerene Blends: Influence of Nanoscale Morphology of Organic Photovoltaic Materials on Charge Recombination to the Triplet State

    Directory of Open Access Journals (Sweden)

    René M. Williams

    2017-01-01

    Full Text Available Femtosecond transient absorption spectroscopy of thin films of two types of morphologies of diketopyrrolopyrrole low band gap polymer/fullerene-adduct blends is presented and indicates triplet state formation by charge recombination, an important loss channel in organic photovoltaic materials. At low laser fluence (approaching solar intensity charge formation characterized by a 1350 nm band (in ~250 fs dominates in the two PDPP-PCBM blends with different nanoscale morphologies and these charges recombine to form a local polymer-based triplet state on the sub-ns timescale (in ~300 and ~900 ps indicated by an 1100 nm absorption band. The rate of triplet state formation is influenced by the morphology. The slower rate of charge recombination to the triplet state (in ~900 ps belongs to a morphology that results in a higher power conversion efficiency in the corresponding device. Nanoscale morphology not only influences interfacial area and conduction of holes and electrons but also influences the mechanism of intersystem crossing (ISC. We present a model that correlates morphology to the exchange integral and fast and slow mechanisms for ISC (SOCT-ISC and H-HFI-ISC. For the pristine polymer, a flat and unstructured singlet-singlet absorption spectrum (between 900 and 1400 nm and a very minor triplet state formation (5% are observed at low laser fluence.

  10. Ion implantation in conjugated polymers: mechanisms for generation of charge carriers

    Energy Technology Data Exchange (ETDEWEB)

    Moliton, A.; Lucas, B.; Moreau, C. (Limoges Univ., 87 (France)); Friend, R.H. (Cambridge Univ. (United Kingdom). Cavendish Lab.); Francois, B. (Institut Charles-Sandron (CNRS), Strasbourg (France))

    1994-06-01

    Ion implantation in conjugated polymers can produce both doping (with suitable choice of ions) and damage in the form of broken covalent bonds. We consider the electronic and transport properties as assessed from measurements on poly(paraphenylene) of d.c. conductivity, thermopower and a.c. conductivity studied against temperature for various implantation parameters. Damage is produced at high implantation energies and high doses, and we find that transport phenomena occur mainly in degenerate states near the Fermi energy, exhibiting a p-type thermopower. We propose a model in which the sp[sup 2] [sigma]-dangling-bond states formed as a result of bond scission are filled from the [pi] valence band. This partial emptying of the valence band is consistent with the transport properties. Lower implantation doses at lower energies induce doping in polaronic bands, with both p-type and n-type thermopower, depending on the ion implanted, although the effects of the defects present can appear, especially at low temperatures. (Author).

  11. Large scale simulation of liquid water transport in a gas diffusion layer of polymer electrolyte membrane fuel cells using the lattice Boltzmann method

    Science.gov (United States)

    Sakaida, Satoshi; Tabe, Yutaka; Chikahisa, Takemi

    2017-09-01

    A method for the large-scale simulation with the lattice Boltzmann method (LBM) is proposed for liquid water movement in a gas diffusion layer (GDL) of polymer electrolyte membrane fuel cells. The LBM is able to analyze two-phase flows in complex structures, however the simulation domain is limited due to heavy computational loads. This study investigates a variety means to reduce computational loads and increase the simulation areas. One is applying an LBM treating two-phases as having the same density, together with keeping numerical stability with large time steps. The applicability of this approach is confirmed by comparing the results with rigorous simulations using actual density. The second is establishing the maximum limit of the Capillary number that maintains flow patterns similar to the precise simulation; this is attempted as the computational load is inversely proportional to the Capillary number. The results show that the Capillary number can be increased to 3.0 × 10-3, where the actual operation corresponds to Ca = 10-5∼10-8. The limit is also investigated experimentally using an enlarged scale model satisfying similarity conditions for the flow. Finally, a demonstration is made of the effects of pore uniformity in GDL as an example of a large-scale simulation covering a channel.

  12. Numerical simulation of liquid water and gas flow in a channel and a simplified gas diffusion layer model of polymer electrolyte membrane fuel cells using the lattice Boltzmann method

    OpenAIRE

    Tabe, Yutaka; Lee, Yongju; Chikahisa, Takemi; Kozakai, Masaya

    2009-01-01

    Numerical simulations using the lattice Boltzmann method (LBM) are developed to elucidate the dynamic behavior of condensed water and gas flow in a polymer electrolyte membrane (PEM) fuel cell. Here, the calculation process of the LBM simulation is improved to extend the simulation to a porous medium like a gas diffusion layer (GDL), and a stable and reliable simulation of two-phase flow with large density differences in the porous medium is established. It is shown that dynamic capillary fin...

  13. Synthesis and Mechanism Insight of a Peptide-Grafted Hyperbranched Polymer Nanosheet with Weak Positive Charges but Excellent Intrinsically Antibacterial Efficacy.

    Science.gov (United States)

    Gao, Jingyi; Wang, Mingzhi; Wang, Fangyingkai; Du, Jianzhong

    2016-06-13

    Antimicrobial resistance is an increasingly problematic issue in the world and there is a present and urgent need to develop new antimicrobial therapies without drug resistance. Antibacterial polymers are less susceptible to drug resistance but they are prone to inducing serious side effects due to high positive charge. Herein we report a peptide-grafted hyperbranched polymer which can self-assemble into unusual nanosheets with highly effective intrinsically antibacterial activity but weak positive charges (+ 6.1 mV). The hyperbranched polymer was synthesized by sequential Michael addition-based thiol-ene and free radical mediated thiol-ene reactions, and followed by ring-opening polymerization of N-carboxyanhydrides (NCAs). The nanosheet structure was confirmed by transmission electron microscopy (TEM) and atomic force microscopy (AFM) studies. Furthermore, a novel "wrapping and penetrating" antibacterial mechanism of the nanosheets was revealed by TEM and it is the key to significantly decrease the positive charges but have a very low minimum inhibitory concentration (MIC) of 16 μg mL(-1) against typical Gram-positive and Gram-negative bacteria. Overall, our synthetic strategy demonstrates a new insight for synthesizing antibacterial nanomaterials with weak positive charges. Moreover, the unique antibacterial mechanism of our nanosheets may be extended for designing next-generation antibacterial agents without drug resistance.

  14. The effect of phase morphology on the nature of long-lived charges in semiconductor polymer:fullerene systems

    KAUST Repository

    Dou, Fei

    2015-01-01

    In this work, we investigate the effect of phase morphology on the nature of charges in poly(2,5-bis(3-tetradecyl-thiophen-2-yl)thieno[3,2,-b]thiophene) (pBTTT-C16) and phenyl-C61-butyric acid methyl ester (PC61BM) blends over timescales greater than hundreds of microseconds by quasi-steady-state photoinduced absorption spectroscopy. Specifically, we compare an essentially fully intermixed, one-phase system based on a 1 : 1 (by weight) pBTTT-C16 : PC61BM blend, known to form a co-crystal structure, with a two-phase morphology composed of relatively material-pure domains of the neat polymer and neat fullerene. The co-crystal occurs at a composition of up to 50 wt% PC61BM, because pBTTT-C16 is capable of hosting fullerene derivatives such as PC61BM in the cavities between its side chains. In contrast, the predominantly two-phase system can be obtained by manipulating a 1 : 1 polymer : fullerene blend with the assistance of a fatty acid methyl ester (dodecanoic acid methyl ester, Me12) as additive, which hinders co-crystal formation. We find that triplet excitons and polarons are generated in both phase morphologies. However, polarons are generated in the predominantly two-phase system at higher photon energy than for the structure based on the co-crystal phase. By means of a quasi-steady-state solution of a mesoscopic rate model, we demonstrate that the steady-state polaron generation efficiency and recombination rates are higher in the finely intermixed, one-phase system compared to the predominantly phase-pure, two-phase morphology. We suggest that the polarons generated in highly intermixed structures, such as the co-crystal investigated here, are localised polarons while those generated in the phase-separated polymer and fullerene systems are delocalised polarons. We expect this picture to apply generally to other organic-based heterojunctions of complex phase morphologies including donor:acceptor systems that form, for instance, molecularly mixed amorphous solid

  15. Extraction of high charge density of states in electrolyte-gated polymer thin-film transistor with temperature-dependent measurements

    Science.gov (United States)

    Lee, Jiyoul

    2016-05-01

    Using temperature-dependent charge transport measurements, we investigated spectral density of states (DOS) in the bandgap of polythiophene thin-films under high carrier densities (Meyer-Neldel rule. The spectral DOS extracted from the electrolyte-gated polymer film lie in the range of 8.0 × 1019 cm-3 eV-1-8.0 × 1021 cm-3 eV-1, which are at least two orders of magnitude larger than the DOS extracted from the same polymer film at relatively low induced carrier densities by general oxide dielectrics.

  16. Controlling charge injection properties in polymer field-effect transistors by incorporation of solution processed molybdenum trioxide.

    Science.gov (United States)

    Long, Dang Xuan; Xu, Yong; Wei, Huai-xin; Liu, Chuan; Noh, Yong-Young

    2015-08-21

    A simply and facilely synthesized MoO3 solution was developed to fabricate charge injection layers for improving the charge-injection properties in p-type organic field-effect transistors (OFETs). By dissolving MoO3 powder in ammonium (NH3) solvent under an air atmosphere, an intermediate ammonium molybdate ((NH4)2MoO4) precursor is made stable, transparent and spin-coated to form the MoO3 interfacial layers, the thickness and morphology of which can be well-controlled. When the MoO3 layer was applied to OFETs with a cost-effective molybdenum (Mo) electrode, the field-effect mobility (μFET) was significantly improved to 0.17 or 1.85 cm(2) V(-1)s(-1) for polymer semiconductors, regioregular poly(3-hexylthiophene) (P3HT) or 3,6-bis-(5bromo-thiophen-2-yl)-N,N'-bis(2-octyl-1-dodecyl)-1,4-dioxo-pyrrolo[3,4-c]pyrrole (DPPT-TT), respectively. Device analysis indicates that the MoO3-deposited Mo contact exhibits a contact resistance RC of 1.2 MΩ cm comparable to that in a device with the noble Au electrode. Kelvin-probe measurements show that the work function of the Mo electrode did not exhibit a dependence on the thickness of MoO3 film. Instead, ultraviolet photoemission spectroscopy results show that a doping effect is probably induced by casting the MoO3 layer on the P3HT semiconductor, which leads to the improved hole injection.

  17. Polymer micelles with hydrophobic core and ionic amphiphilic corona. 1. Statistical distribution of charged and nonpolar units in corona.

    Science.gov (United States)

    Lysenko, Evgeny A; Kulebyakina, Alevtina I; Chelushkin, Pavel S; Rumyantsev, Artem M; Kramarenko, Elena Yu; Zezin, Alexander B

    2012-12-11

    Polymer micelles with hydrophobic polystyrene (PS) core and ionic amphiphilic corona from charged N-ethyl-4-vinylpyridinium bromide (EVP) and uncharged 4-vinylpyridine (4VP) units spontaneously self-assembled from PS-block-poly(4VP-stat-EVP) macromolecules in mixed dimethylformamide/methanol/water solvent. The fraction of statistically distributed EVP units in corona-forming block is β = [EVP]/([EVP]+[4VP]) = 0.3-1. Micelles were transferred into water via dialysis technique, and pH was adjusted to 9, where 4VP is insoluble. Structural characteristics of micelles were investigated both experimentally and theoretically as a function of corona composition β. Methods of dynamic and static light scattering, electrophoretic mobility measurements, sedimentation velocity, transmission electron microscopy, and UV spectrophotometry were applied. All micelles possessed spherical morphology. The aggregation number, structure, and electrophoretic mobility of micelles changed in a jumplike manner near β ~ 0.6-0.75. Below and above this region, micelle characteristics were constant or insignificantly changed upon β. Theoretical dependencies for micelle aggregation number, corona dimensions, and fraction of small counterions outside corona versus β were derived via minimization the micelle free energy, taking into account surface, volume, electrostatic, and elastic contributions of chain units and translational entropy of mobile counterions. Theoretical estimations also point onto a sharp structural transition at a certain corona composition. The abrupt reorganization of micelle structure at β ~ 0.6-0.75 entails dramatic changes in micelle dispersion stability in the presence of NaCl or in the presence of oppositely charged polymeric (sodium polymethacrylate) or amphiphilic (sodium dodecyl sulfate) complexing agents.

  18. Highly-Efficient Charge Separation and Polaron Delocalization in Polymer-Fullerene Bulk-Heterojunctions: A Comparative Multi-Frequency EPR & DFT Study

    Science.gov (United States)

    Niklas, Jens; Mardis, Kristy L.; Banks, Brian P.; Grooms, Gregory M.; Sperlich, Andreas; Dyakonov, Vladimir; Beaupré, Serge; Leclerc, Mario; Xu, Tao; Yu, Luping; Poluektov, Oleg G.

    2016-01-01

    The ongoing depletion of fossil fuels has led to an intensive search for additional renewable energy sources. Solar-based technologies could provide sufficient energy to satisfy the global economic demands in the near future. Photovoltaic (PV) cells are the most promising man-made devices for direct solar energy utilization. Understanding the charge separation and charge transport in PV materials at a molecular level is crucial for improving the efficiency of the solar cells. Here, we use light-induced EPR spectroscopy combined with DFT calculations to study the electronic structure of charge separated states in blends of polymers (P3HT, PCDTBT, and PTB7) and fullerene derivatives (C60-PCBM and C70-PCBM). Solar cells made with the same composites as active layers show power conversion efficiencies of 3.3% (P3HT), 6.1% (PCDTBT), and 7.3% (PTB7), respectively. Under illumination of these composites, two paramagnetic species are formed due to photo-induced electron transfer between the conjugated polymer and the fullerene. They are the positive, P+, and negative, P-, polarons on the polymer backbone and fullerene cage, respectively, and correspond to radical cations and radical anions. Using the high spectral resolution of high-frequency EPR (130 GHz), the EPR spectra of these species were resolved and principal components of the g-tensors were assigned. Light-induced pulsed ENDOR spectroscopy allowed the determination of 1H hyperfine coupling constants of photogenerated positive and negative polarons. The experimental results obtained for the different polymer-fullerene composites have been compared with DFT calculations, revealing that in all three systems the positive polaron is distributed over distances of 40 - 60 Å on the polymer chain. This corresponds to about 15 thiophene units for P3HT, approximately three units PCDTBT, and about three to four units for PTB7. No spin density delocalization between neighboring fullerene molecules was detected by EPR. Strong

  19. Highly-efficient charge separation and polaron delocalization in polymer-fullerene bulk-heterojunctions: a comparative multi-frequency EPR and DFT study.

    Science.gov (United States)

    Niklas, Jens; Mardis, Kristy L; Banks, Brian P; Grooms, Gregory M; Sperlich, Andreas; Dyakonov, Vladimir; Beaupré, Serge; Leclerc, Mario; Xu, Tao; Yu, Luping; Poluektov, Oleg G

    2013-06-28

    The ongoing depletion of fossil fuels has led to an intensive search for additional renewable energy sources. Solar-based technologies could provide sufficient energy to satisfy the global economic demands in the near future. Photovoltaic (PV) cells are the most promising man-made devices for direct solar energy utilization. Understanding the charge separation and charge transport in PV materials at a molecular level is crucial for improving the efficiency of the solar cells. Here, we use light-induced EPR spectroscopy combined with DFT calculations to study the electronic structure of charge separated states in blends of polymers (P3HT, PCDTBT, and PTB7) and fullerene derivatives (C60-PCBM and C70-PCBM). Solar cells made with the same composites as active layers show power conversion efficiencies of 3.3% (P3HT), 6.1% (PCDTBT), and 7.3% (PTB7), respectively. Upon illumination of these composites, two paramagnetic species are formed due to photo-induced electron transfer between the conjugated polymer and the fullerene. They are the positive, P(+), and negative, P(-), polarons on the polymer backbone and fullerene cage, respectively, and correspond to radical cations and radical anions. Using the high spectral resolution of high-frequency EPR (130 GHz), the EPR spectra of these species were resolved and principal components of the g-tensors were assigned. Light-induced pulsed ENDOR spectroscopy allowed the determination of (1)H hyperfine coupling constants of photogenerated positive and negative polarons. The experimental results obtained for the different polymer-fullerene composites have been compared with DFT calculations, revealing that in all three systems the positive polaron is distributed over distances of 40-60 Å on the polymer chain. This corresponds to about 15 thiophene units for P3HT, approximately three units for PCDTBT, and about three to four units for PTB7. No spin density delocalization between neighboring fullerene molecules was detected by EPR

  20. Direct and charge transfer state mediated photogeneration in polymer-fullerene bulk heterojunction solar cells

    Science.gov (United States)

    Mingebach, M.; Walter, S.; Dyakonov, V.; Deibel, C.

    2012-05-01

    We investigated photogeneration yield and recombination dynamics in blends of poly(3-hexyl thiophene) (P3HT) and poly[2-methoxy-5 -(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) with [6,6]-phenyl-C61butyric acid methyl ester (PC61BM) by means of temperature dependent time delayed collection field measurements. In MDMO-PPV:PC61BM, we find a strongly field dependent polaron pair dissociation which can be attributed to geminate recombination in the device. Our findings are in good agreement with field dependent photoluminescence measurements published before, supporting a scenario of polaron pair dissociation via an intermediate charge transfer state. In contrast, polaron pair dissociation in P3HT:PC61BM shows only a very weak field dependence, indicating an almost field independent polaron pair dissociation or a direct photogeneration. Furthermore, we found Langevin recombination for MDMO-PPV:PC61BM and strongly reduced Langevin recombination for P3HT:PC61BM.

  1. Dual Functional Polymer Interlayer for Facilitating Ion Transport and Reducing Charge Recombination in Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Wang, Ying-Chiao; Li, Shao-Sian; Wen, Cheng-Yen; Chen, Liang-Yih; Ho, Kuo-Chuan; Chen, Chun-Wei

    2016-12-14

    Dye-sensitized solar cells (DSSCs) present low-cost alternatives to conventional wafer-based inorganic solar cells and have remarkable power conversion efficiency. To further enhance performance, we propose a new DSSC architecture with a novel dual-functional polymer interlayer that prevents charge recombination and facilitates ionic conduction, as well as maintaining dye loading and regeneration. Poly(vinylidene fluoride-trifluoroethylene) (p(VDF-TrFE)) was coated on the outside of a dye-sensitized TiO2 photoanode by a simple solution process that did not sacrifice the amount of adsorbed dye molecules in the DSSC device. Light-intensity-modulated photocurrent and photovoltage spectroscopy revealed that the proposed p(VDF-TrFE)-coated anode yielded longer electron lifetime and improved the injection of photogenerated electrons into TiO2, thereby reducing the electron transport time. Comparative cyclic voltammetry and UV-visible absorption spectroscopy based on a ferrocene-ferrocenium external standard material demonstrated that p(VDF-TrFE) enhanced the power conversion efficiency from 7.67% to 9.11%. This dual functional p(VDF-TrFE) interlayer is a promising candidate for improving the performance of DSSCs and can also be employed in other electrochemical devices.

  2. Interplay of electrostatics and lipid packing determines the binding of charged polymer coated nanoparticles to model membranes.

    Science.gov (United States)

    Biswas, Nupur; Bhattacharya, Rupak; Saha, Arindam; Jana, Nikhil R; Basu, Jaydeep K

    2015-10-07

    Understanding of nanoparticle-membrane interactions is useful for various applications of nanoparticles like drug delivery and imaging. Here we report on the studies of interaction between hydrophilic charged polymer coated semiconductor quantum dot nanoparticles with model lipid membranes. Atomic force microscopy and X-ray reflectivity measurements suggest that cationic nanoparticles bind and penetrate bilayers of zwitterionic lipids. Penetration and binding depend on the extent of lipid packing and result in the disruption of the lipid bilayer accompanied by enhanced lipid diffusion. On the other hand, anionic nanoparticles show minimal membrane binding although, curiously, their interaction leads to reduction in lipid diffusivity. It is suggested that the enhanced binding of cationic QDs at higher lipid packing can be understood in terms of the effective surface potential of the bilayers which is tunable through membrane lipid packing. Our results bring forth the subtle interplay of membrane lipid packing and electrostatics which determine nanoparticle binding and penetration of model membranes with further implications for real cell membranes.

  3. Charge-discharge studies on a lithium cell composed of PVdF-HFP polymer membranes prepared by phase inversion technique with a nanocomposite cathode

    Science.gov (United States)

    Manuel Stephan, A.; Teeters, Dale

    A novel polymer membrane of poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) co-polymer was prepared by the phase inversion technique with two different non-solvents, 1-butanol or hexane. The prepared films were analyzed by scanning electron microscope (SEM) and nitrogen absorption/desorption techniques. The change in the morphology and pore diameter of the films prepared with different non-solvents correlates with the structure of the non-solvents used. This electrolyte membrane was coupled with a nanocomposite LiAl 0.01Co 0.99O 2 cathode which was prepared by a solid-state reaction method and subsequently by ball-milling. Lithium cells consisting of LiAl 0.01Co 0.99O 2/polymer electrolyte/Li were assembled and their charge-discharge studies were investigated.

  4. Impact of Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation (RIR-MAPLE) on Morphology and Charge Conduction in Conjugated Polymer and Bulk Heterojunction Thin Films

    Science.gov (United States)

    Stiff-Roberts, Adrienne; McCormick, Ryan; Atewologun, Ayomide

    2014-03-01

    An approach to improve organic photovoltaic efficiency is to increase vertical charge conduction by promoting out-of-plane π- π stacking in conjugated polymers. Resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) features multiple growth parameters that can be varied to achieve a desired organic thin film property. In addition, RIR-MAPLE enables nanoscale domains in blended polymeric films and multi-layer polymeric films regardless of constituent solubility. Thus, RIR-MAPLE deposition is compared to solution-cast films as a possible approach to increase out-of-plane charge transport in polymers and bulk heterojunctions. Two common, solar cell polymers are investigated: P3HT and PCPDTBT. Materials characterization includes grazing-incidence, wide angle x-ray scattering (GIWAXS) for structural information and two techniques to determine hole mobility: organic field effect transistors to measure in-plane mobility and charge extraction by linearly increasing voltage to measure out-of-plane mobility. Initial indications are that the RIR-MAPLE films have a fundamentally different morphology compared to solution-cast films. In the case of P3HT, an enhancement in out-of-plane π- π stacking was observed by GIWAXS in RIR-MAPLE films compared to solution-cast films. A portion of this research was conducted at CNMS at ORNL.

  5. Interactions of silica nanoparticles with poly(ethylene oxide) and poly(acrylic acid): effect of the polymer molecular weight and of the surface charge.

    Science.gov (United States)

    Joksimovic, R; Prévost, S; Schweins, R; Appavou, M-S; Gradzielski, M

    2013-03-15

    The properties and the structure of polymer-modified silica nanoparticles were investigated by several characterization methods, with an emphasis on scattering techniques. Both bare and amino functionalized nanoparticles were used. To determine the effect of the charge, the polymer used was either nonionic poly(ethylene oxide) (PEO) or partially deprotonated poly(acrylic acid) (PAA). The particles coated with PEO were investigated by small-angle neutron scattering using the method of external contrast variation to observe the polymer coverage. The quantity adsorbed was found to be increasing with the molecular weight, and the surface type, bare or aminated, did not have a significant influence on the quantity adsorbed. The adsorption of PAA on positively charged aminated particles was investigated by dynamic light scattering and zeta potential measurements. A charge reversal, from positive to negative, was induced by the presence of PAA. Through the derivation of the structure factor, small-angle X-ray scattering provided significant information on the formation of aggregates at low PAA concentrations.

  6. Reversible Charge Trapping in Bis-Carbazole-Diimide Redox Polymers with Complete Luminescence Quenching Enabling Nondestructive Read-Out by Resonance Raman Spectroscopy

    Science.gov (United States)

    2017-01-01

    The coupling of substituted carbazole compounds through carbon–carbon bond formation upon one-electron oxidation is shown to be a highly versatile approach to the formation of redox polymer films. Although the polymerization of single carbazole units has been proposed earlier, we show that by tethering pairs of carbazoles double sequential dimerization allows for facile formation of redox polymer films with fine control over film thickness. We show that the design of the monomers and in particular the bridging units is key to polymer formation, with the diaminobenzene motif proving advantageous, in terms of the matching to the redox potentials of the monomer and polymer film and thereby avoiding limitations in film thickness (autoinsulation), but introduces unacceptable instability due to the intrinsic redox activity of this moiety. The use of a diimide protecting group both avoids complications due to p-diamino-benzene redox chemistry and provides for a redox polymer in which the photoluminescence of the bis-carbazole moiety can be switched reversibly (on/off) with redox control. The monomer design approach is versatile enabling facile incorporation of additional functional units, such as naphthalene. Here we show that a multicomponent carbazole/naphthalene containing monomer (APCNDI) can form redox polymer films showing both p- and n- conductivity under ambient conditions and allows access to five distinct redox states, and a complex electrochromic response covering the whole of the UV/vis–NIR spectral region. The highly effective quenching of the photoluminescence of both components in poly-APCNDI enables detailed characterization of the redox polymer films. The poly-APCNDI films show extensive charge trapping, which can be read out spectroscopically in the case of films and is characterized as kinetic rather than chemical in origin on the basis of UV/vis–NIR absorption and resonance Raman spectroscopic analyses. The strong resonantly enhanced Raman

  7. Efficient charge injection in p-type polymer field-effect transistors with low-cost molybdenum electrodes through V2O5 interlayer.

    Science.gov (United States)

    Baeg, Kang-Jun; Bae, Gwang-Tae; Noh, Yong-Young

    2013-06-26

    Here we report high-performance polymer OFETs with a low-cost Mo source/drain electrode by efficient charge injection through the formation of a thermally deposited V2O5 thin film interlayer. A thermally deposited V2O5 interlayer is formed between a regioregular poly(3-hexylthiophene) (rr-P3HT) or a p-type polymer semiconductor containing dodecyl-substituted thienylenevinylene (TV) and dodecylthiophene (PC12TV12T) and the Mo source/drain electrode. The P3HT or PC12TV12T OFETs with the bare Mo electrode exhibited lower charge carrier mobility than those with Au owing to a large barrier height for hole injection (0.5-1.0 eV). By forming the V2O5 layer, the P3HT or PC12TV12T OFETs with V2O5 on the Mo electrode exhibited charge carrier mobility comparable to that of a pristine Au electrode. Best P3HT or PC12TV12T OFETs with 5 nm thick V2O5 on Mo electrode show the charge carrier mobility of 0.12 and 0.38 cm(2)/(V s), respectively. Ultraviolet photoelectron spectroscopy results exhibited the work-function of the Mo electrode progressively changed from 4.3 to 4.9 eV with an increase in V2O5 thickness from 0 to 5 nm, respectively. Interestingly, the V2O5-deposited Mo exhibits comparable Rc to Au, which mainly results from the decreased barrier height for hole carrier injection from the low-cost metal electrode to the frontier molecular orbital of the p-type polymer semiconductor after the incorporation of the transition metal oxide hole injection layer, such as V2O5. This enables the development of large-area, low-cost electronics with the Mo electrodes and V2O5 interlayer.

  8. Phase behavior and molecular thermodynamics of coacervation in oppositely charged polyelectrolyte/surfactant systems: a cationic polymer JR 400 and anionic surfactant SDS mixture.

    Science.gov (United States)

    Li, Dongcui; Kelkar, Manish S; Wagner, Norman J

    2012-07-17

    Coacervation in mixtures of polyelectrolytes and surfactants with opposite charge is common in nature and is also technologically important to consumer health care products. To understand the complexation behavior of these systems better, we combine multiple experimental techniques to systematically study the polymer/surfactant binding interactions and the phase behavior of anionic sodium dodecyl sulfate (SDS) surfactant in cationic JR 400 polymer aqueous solutions. The phase-behavior study resolves a discrepancy in the literature by identifying a metastable phase between the differing redissolution phase boundaries reported in the literature for the surfactant-rich regime. Isothermal titration calorimetry analyzed within the framework of the simple Satake-Yang model identifies binding parameters for the surfactant-lean phase, whereas a calculation for polymer-bound micelles coexisting with free micelles is analyzed in the surfactant-rich redissolution regime. This analysis provides a preliminary understanding of the interactions governing the observed phase behavior. The resulting thermodynamic properties, including binding constants and the molar Gibbs free energies, enthalpies, and entropies, identify the relative importance of both hydrophobic and electrostatic interactions and provide a first approximation for the corresponding microstructures in the different phases. Our study also addresses the stability and metastability of oppositely charged polyelectrolytes and surfactant mixtures.

  9. Lattice Bosons

    CERN Document Server

    Chakrabarti, J; Bagchi, B; Chakrabarti, Jayprokas; Basu, Asis; Bagchi, Bijon

    2000-01-01

    Fermions on the lattice have bosonic excitations generated from the underlying periodic background. These, the lattice bosons, arise near the empty band or when the bands are nearly full. They do not depend on the nature of the interactions and exist for any fermion-fermion coupling. We discuss these lattice boson solutions for the Dirac Hamiltonian.

  10. Charge Separation in Intermixed Polymer:PC70BM Photovoltaic Blends: Correlating Structural and Photophysical Length Scales as a Function of Blend Composition

    KAUST Repository

    Utzat, Hendrik

    2017-04-24

    A key challenge in achieving control over photocurrent generation by bulk-heterojunction organic solar cells is understanding how the morphology of the active layer impacts charge separation and in particular the separation dynamics within molecularly intermixed donor-acceptor domains versus the dynamics between phase-segregated domains. This paper addresses this issue by studying blends and devices of the amorphous silicon-indacenodithiophene polymer SiIDT-DTBT and the acceptor PCBM. By changing the blend composition, we modulate the size and density of the pure and intermixed domains on the nanometer length scale. Laser spectroscopic studies show that these changes in morphology correlate quantitatively with the changes in charge separation dynamics on the nanosecond time scale and with device photocurrent densities. At low fullerene compositions, where only a single, molecularly intermixed polymer-fullerene phase is observed, photoexcitation results in a ∼ 30% charge loss from geminate polaron pair recombination, which is further studied via light intensity experiments showing that the radius of the polaron pairs in the intermixed phase is 3-5 nm. At high fullerene compositions (≥67%), where the intermixed domains are 1-3 nm and the pure fullerene phases reach ∼4 nm, the geminate recombination is suppressed by the reduction of the intermixed phase, making the fullerene domains accessible for electron escape.

  11. From Recombination Dynamics to Device Performance: Quantifying the Efficiency of Exciton Dissociation, Charge Separation, and Extraction in Bulk Heterojunction Solar Cells with Fluorine-Substituted Polymer Donors

    KAUST Repository

    Gorenflot, Julien

    2017-09-28

    An original set of experimental and modeling tools is used to quantify the yield of each of the physical processes leading to photocurrent generation in organic bulk heterojunction solar cells, enabling evaluation of materials and processing condition beyond the trivial comparison of device performances. Transient absorption spectroscopy, “the” technique to monitor all intermediate states over the entire relevant timescale, is combined with time-delayed collection field experiments, transfer matrix simulations, spectral deconvolution, and parametrization of the charge carrier recombination by a two-pool model, allowing quantification of densities of excitons and charges and extrapolation of their kinetics to device-relevant conditions. Photon absorption, charge transfer, charge separation, and charge extraction are all quantified for two recently developed wide-bandgap donor polymers: poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-difluorothiophene) (PBDT[2F]T) and its nonfluorinated counterpart poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-thiophene) (PBDT[2H]T) combined with PC71BM in bulk heterojunctions. The product of these yields is shown to agree well with the devices\\' external quantum efficiency. This methodology elucidates in the specific case studied here the origin of improved photocurrents obtained when using PBDT[2F]T instead of PBDT[2H]T as well as upon using solvent additives. Furthermore, a higher charge transfer (CT)-state energy is shown to lead to significantly lower energy losses (resulting in higher VOC) during charge generation compared to P3HT:PCBM.

  12. Radical polymer-wrapped SWNTs at a molecular level: High-rate redox mediation through a percolation network for a transparent charge-storage material

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Wonsung; Nishide, Hiroyuki [Department of Applied Chemistry, Waseda University, Tokyo 169-8555 (Japan); Department of Nanobio Materials and Electronics (WCU), Gwangju Institute of Science and Technology(GIST), Gwangju 500-712 (Korea, Republic of); Ohtani, Shota; Oyaizu, Kenichi [Department of Applied Chemistry, Waseda University, Tokyo 169-8555 (Japan); Geckeler, Kurt E. [Department of Nanobio Materials and Electronics (WCU), Gwangju Institute of Science and Technology(GIST), Gwangju 500-712 (Korea, Republic of)

    2011-10-11

    A transparent nanocomposite of a radical polymer, the poly(2,2,6,6-tetramethylpiperidine-1-oxy-4-yl methacrylate) (PTMA), and single-walled carbon nanotubes (SWNTs) display a reversible charging and discharging, allowing for full discharging in seconds. This is ascribed to the reversible electrochemical reaction of the pendant radical group in PTMA aided by both PTMA wrapping at a molecular level and the SWNT network for electrical conduction. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Silicon Nanowire/Polymer Hybrid Solar Cell-Supercapacitor: A Self-Charging Power Unit with a Total Efficiency of 10.5.

    Science.gov (United States)

    Liu, Ruiyuan; Wang, Jie; Sun, Teng; Wang, Mingjun; Wu, Changsheng; Zou, Haiyang; Song, Tao; Zhang, Xiaohong; Lee, Shuit-Tong; Wang, Zhong Lin; Sun, Baoquan

    2017-07-12

    An integrated self-charging power unit, combining a hybrid silicon nanowire/polymer heterojunction solar cell with a polypyrrole-based supercapacitor, has been demonstrated to simultaneously harvest solar energy and store it. By efficiency enhancement of the hybrid nanowire solar cells and a dual-functional titanium film serving as conjunct electrode of the solar cell and supercapacitor, the integrated system is able to yield a total photoelectric conversion to storage efficiency of 10.5%, which is the record value in all the integrated solar energy conversion and storage system. This system may not only serve as a buffer that diminishes the solar power fluctuations from light intensity, but also pave its way toward cost-effective high efficiency self-charging power unit. Finally, an integrated device based on ultrathin Si substrate is demonstrated to expand its feasibility and potential application in flexible energy conversion and storage devices.

  14. Positively charged polymers modulate the fate of human mesenchymal stromal cells via ephrinB2/EphB4 signaling

    Directory of Open Access Journals (Sweden)

    Ilenia De Luca

    2016-09-01

    Full Text Available Understanding the mechanisms by which mesenchymal stromal cells (MSCs interact with the physical properties (e.g. topography, charge, ζ-potential, and contact angle of polymeric surfaces is essential to design new biomaterials capable of regulating stem cell behavior. The present study investigated the ability of two polymers (pHM1 and pHM3 with different positive surface charge densities to modulate the differentiation of MSCs into osteoblast-like phenotype via cell-cell ephrinB2/EphB4 signaling. Although pHM1 promoted the phosphorylation of EphB4, leading to cell differentiation, pHM3, characterized by a high positive surface charge density, had no significant effect on EphB4 activation or MSCs differentiation. When the MSCs were cultured on pHM1 in the presence of a forward signaling blocking peptide, the osteoblast differentiation was compromised. Our results demonstrated that the ephrinB2/EphB4 interaction was required for MSCs differentiation into an osteoblast-like phenotype and that the presence of a high positive surface charge density altered this interaction.

  15. Investigation of electric charge transport in conjugated polymer P3HT: PCBM solar cell with temperature dependent current and capacitance measurements

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Peiqing; Mencaraglia, Denis; Darga, Arouna; Migan, Anne [Laboratoire de Genie Electrique de Paris, CNRS UMR 8507, SUPELEC, UPMC, Universite Paris VI, Universite Paris-Sud, 11 Rue Joliot Curie, Plateau de Moulon, 91192 Gif-Sur-Yvette Cedex (France); Rabdbeh, Roshanak; Ratier, Bernard; Moliton, Andre [Institut Carnot XLim, UMR 6172, CNRS, Universite de Limoges, 123 Avenue Albert Thomas, 87060 Limoges Cedex (France)

    2010-04-15

    We investigated quantitatively the electronic transport properties of a bulk heterojunction polymer/fullerene solar cell, based on structure Glass/ITO/P3HT:PCBM/Al. The current-voltage I-V characteristics in the intermediate positive bias and temperature regime (0.2 V {<=} V {<=} 1.5 V, 180 K {<=} T {<=} 250 K) can be well fitted by a modified Poole-Frenkel PF detrapping model. Combining these results with the high frequency capacitance measurements, we could then derive independently the absorber thickness and its dielectric constant. At low temperature (80 K {<=} T {<=} 170 K), the I-V data can be well accounted for with Space Charge Limited Current (SCLC) regimes. At intermediate positive bias (1 V {<=} V {<=} 2.3 V), the current is dominated by the trapped space charges with an exponential traps distribution, while at high positive bias (2.5 V {<=} V {<=} 4 V), the space charges due to injected free carrier play an important role for the conduction. From the fits to the two different SCLC models, we could then extract the electrically active defects parameters controlling the transport. These parameters were confirmed by space charge capacitance spectroscopy (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Highly reliable top-gated thin-film transistor memory with semiconducting, tunneling, charge-trapping, and blocking layers all of flexible polymers.

    Science.gov (United States)

    Wang, Wei; Hwang, Sun Kak; Kim, Kang Lib; Lee, Ju Han; Cho, Suk Man; Park, Cheolmin

    2015-05-27

    The core components of a floating-gate organic thin-film transistor nonvolatile memory (OTFT-NVM) include the semiconducting channel layer, tunneling layer, floating-gate layer, and blocking layer, besides three terminal electrodes. In this study, we demonstrated OTFT-NVMs with all four constituent layers made of polymers based on consecutive spin-coating. Ambipolar charges injected and trapped in a polymer electret charge-controlling layer upon gate program and erase field successfully allowed for reliable bistable channel current levels at zero gate voltage. We have observed that the memory performance, in particular the reliability of a device, significantly depends upon the thickness of both blocking and tunneling layers, and with an optimized layer thickness and materials selection, our device exhibits a memory window of 15.4 V, on/off current ratio of 2 × 10(4), read and write endurance cycles over 100, and time-dependent data retention of 10(8) s, even when fabricated on a mechanically flexible plastic substrate.

  17. The effect of surface hydrogenation of metal oxides on the nanomorphology and the charge generation efficiency of polymer blend solar cells

    Science.gov (United States)

    Vasilopoulou, Maria

    2014-10-01

    In this work, the effect of surface hydrogenation of different metal oxides, in particular molybdenum and tungsten oxides widely used to enhance hole extraction and zinc and titanium oxides widely used to enhance electron extraction, on the nanomorphology and the charge generation efficiency of polymer blend solar cells is investigated. It was found that photoactive layers based on blends using different polymers, in particular poly(3-hexythiophene) (P3HT) and poly[(9-(1-octylnonyl)-9H-carbazole-2,7-diyl)-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT), which normally differ in both morphology and electronic structure, benefited, for both polymers, from deposition on metal oxides with high surface hydrogen content, in the sense that they exhibited improved crystallinity/order as revealed from X-ray diffraction, UV-vis absorption and elipsometric measurements. As a result, increased charge generation efficiencies and reduced recombination losses were measured in solar cells using metal oxides with highly hydrogenated surfaces at bottom electrodes and based on blends of either P3HT or PCDTBT, with a fullerene acceptor, as was verified by transient photocurrent measurements. The power conversion efficiency (PCE) of those cells reached values of 4.5% and 7.2%, respectively, an increase of about 30% compared with the cells using metal oxides with low surface hydrogen content.In this work, the effect of surface hydrogenation of different metal oxides, in particular molybdenum and tungsten oxides widely used to enhance hole extraction and zinc and titanium oxides widely used to enhance electron extraction, on the nanomorphology and the charge generation efficiency of polymer blend solar cells is investigated. It was found that photoactive layers based on blends using different polymers, in particular poly(3-hexythiophene) (P3HT) and poly[(9-(1-octylnonyl)-9H-carbazole-2,7-diyl)-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2

  18. Diketopyrrolopyrrole-based Conjugated Polymer Entailing Triethylene Glycols as Side Chains with High Thin Film Charge Mobility without Post-Treatments.

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Si-Fen; Liu, Zitong; Cai, Zheng-Xu; Dyson, Matthew J.; Stingelin, Natalie; Chen, Wei; Ju, Hua-Jun; Zhang, Guan-Xin; Zhang, De-Qing

    2017-08-01

    Side chain engineering of conjugated donor-acceptor polymers is a new way to manipulate their optoelectronic properties. Two new diketopyrrolopyrrole (DPP)-terthiophene-based conjugated polymers PDPP3T-1 and PDPP3T-2, with both hydrophilic triethylene glycol (TEG) and hydrophobic alkyl chains, are reported. It is demonstrated that the incorporation of TEG chains has a significant effect on the interchain packing and thin-film morphology with noticeable effect on charge transport. Polymer chains of PDPP3T-1 in which TEG chains are uniformly distributed can self-assemble spontaneously into a more ordered thin film. As a result, the thin film of PDPP3T-1 exhibits high saturated hole mobility up to 2.6 cm(2) V-1 s(-1) without any post-treatment. This is superior to those of PDPP3T with just alkyl chains and PDPP3T-2. Moreover, the respective field effect transistors made of PDPP3T-1 can be utilized for sensing ethanol vapor with high sensitivity (down to 100 ppb) and good selectivity.

  19. Influence of crystallinity and energetics on charge separation in polymer-inorganic nanocomposite films for solar cells.

    Science.gov (United States)

    Bansal, Neha; Reynolds, Luke X; MacLachlan, Andrew; Lutz, Thierry; Ashraf, Raja Shahid; Zhang, Weimin; Nielsen, Christian B; McCulloch, Iain; Rebois, Dylan G; Kirchartz, Thomas; Hill, Michael S; Molloy, Kieran C; Nelson, Jenny; Haque, Saif A

    2013-01-01

    The dissociation of photogenerated excitons and the subsequent spatial separation of the charges are of crucial importance to the design of efficient donor-acceptor heterojunction solar cells. While huge progress has been made in understanding charge generation at all-organic junctions, the process in hybrid organic:inorganic systems has barely been addressed. Here, we explore the influence of energetic driving force and local crystallinity on the efficiency of charge pair generation at hybrid organic:inorganic semiconductor heterojunctions. We use x-ray diffraction, photoluminescence quenching, transient absorption spectroscopy, photovoltaic device and electroluminescence measurements to demonstrate that the dissociation of photogenerated polaron pairs at hybrid heterojunctions is assisted by the presence of crystalline electron acceptor domains. We propose that such domains encourage delocalization of the geminate pair state. The present findings suggest that the requirement for a large driving energy for charge separation is relaxed when a more crystalline electron acceptor is used.

  20. Superradiance Lattice

    CERN Document Server

    Wang, Da-Wei; Zhu, Shi-Yao; Scully, Marlan O

    2014-01-01

    We show that the timed Dicke states of a collection of three-level atoms can form a tight-binding lattice in the momentum space. This lattice, coined the superradiance lattice (SL), can be constructed based on an electromagnetically induced transparency (EIT) system. For a one-dimensional SL, we need the coupling field of the EIT system to be a standing wave. The detuning between the two components of the standing wave introduces an effective electric field. The quantum behaviours of electrons in lattices, such as Bloch oscillations, Wannier-Stark ladders, Bloch band collapsing and dynamic localization can be observed in the SL. The SL can be extended to two, three and even higher dimensions where no analogous real space lattices exist and new physics are waiting to be explored.

  1. In situ synthesis of polymer-clay nanocomposites from silicate gels.

    Energy Technology Data Exchange (ETDEWEB)

    Carrado, K. A.; Xu, L.; Chemistry

    1998-01-01

    Polymer-containing silicate gels were hydrothermally crystallized to form layered magnesium silicate hectorite clays containing polymers that are incorporated in situ. Gels consist of silica sol, magnesium hydroxide sol, lithium fluoride, and the polymer of choice. Dilute solutions of gel in water are refluxed for various lengths of time and then isolated via centrifugation, washed, and air-dried. Polymer loadings up to 86% were attained by adding more polymer to the solutions after 2-day reaction times, reacting for another 24 h, and continuing this process prior to isolation. Polyaniline (PANI)- and polyacrylonitrile (PACN)-clay samples contain up to 57% and 76% polymer, respectively, after just one sequential addition at high polymer loading. Series of PANI-, PACN-, poly(vinylpyrrolidone) (PVP)-, and hydroxypropylmethylcellulose (HPMC)-clays also were prepared by several sequential additions of lower polymer loading to the silicate gel during crystallization. Final polymer loadings were determined by thermal analysis. Basal spacings between clay interlayers were measured by X-ray powder diffraction for all samples. Increases in polymer loadings and basal spacings were observed for all the neutral polymers studied, until or unless delamination occurred. Delamination was evident for PACN- and PANI-clay nanocomposites. The highest loadings were observed for the PACN-clays, up to 86%. For the cationic polymer polydimethyldiallylammonium chloride, however, the loading could not be increased beyond about 20%. This is due to electrostatic interactions that balance the negatively charged sites on the silicate lattice with those on the cationic polymer chain. Beyond charge compensation, there is no driving force for further incorporation. Charge compensation in the case of the neutral polymers is attained by interlayer lithium(I) cations.

  2. Positively charged polymer brush-functionalized filter paper for DNA sequence determination following Dot blot hybridization employing a pyrrolidinyl peptide nucleic acid probe.

    Science.gov (United States)

    Laopa, Praethong S; Vilaivan, Tirayut; Hoven, Voravee P

    2013-01-07

    As inspired by the Dot blot analysis, a well known technique in molecular biology and genetics for detecting biomolecules, a new paper-based platform for colorimetric detection of specific DNA sequences employing peptide nucleic acid (PNA) as a probe has been developed. In this particular study, a pyrrolidinyl PNA bearing a conformationally rigid d-prolyl-2-aminocyclopentanecarboxylic acid backbone (acpcPNA) was used as a probe. The filter paper was modified to be positively charged with grafted polymer brushes of quaternized poly(dimethylamino)ethyl methacrylate (QPDMAEMA) prepared by surface-initiated polymerization of 2-(dimethylamino)ethyl methacrylate from the filter paper via ARGET ATRP followed by quaternization with methyl iodide. Following the Dot blot format, a DNA target was first immobilized via electrostatic interactions between the positive charges of the QPDMAEMA brushes and negative charges of the phosphate backbone of DNA. Upon hybridization with the biotinylated pyrrolidinyl peptide nucleic acid (b-PNA) probe, the immobilized DNA can be detected by naked eye observation of the yellow product generated by the enzymatic reaction employing HRP-labeled streptavidin. It has been demonstrated that this newly developed assay was capable of discriminating between complementary and single base mismatch targets at a detection limit of at least 10 fmol. In addition, the QPDMAEMA-grafted filter paper exhibited a superior performance to the commercial membranes, namely Nylon 66 and nitrocellulose.

  3. Simple and rapid high performance liquid chromatography method for the determination of polidocanol as bulk product and in pharmaceutical polymer matrices using charged aerosol detection.

    Science.gov (United States)

    Ilko, David; Puhl, Sebastian; Meinel, Lorenz; Germershaus, Oliver; Holzgrabe, Ulrike

    2015-02-01

    Currently, neither the European nor the United States Pharmacopoeia provide a method for the determination of polidocanol (PD) content despite the fact that PD, besides being an excipient, is also used as an active pharmaceutical ingredient. We therefore developed a method where the PD content was determined using a Kinetex C18 column operated at 40°C with water-acetonitrile (15:85, v/v) as mobile phase. A Corona(®) charged aerosol detector was employed for the detection of PD that is lacking a suitable UV chromophore. The method was fully validated. Additionally, the method was applied for the determination of PD release from a pharmaceutical polymer matrix consisting of poly-ɛ-caprolactone and poly(lactic-co-glycolic acid) and PD.

  4. High-Efficiency Aqueous-Processed Polymer/CdTe Nanocrystals Planar Heterojunction Solar Cells with Optimized Band Alignment and Reduced Interfacial Charge Recombination.

    Science.gov (United States)

    Zeng, Qingsen; Hu, Lu; Cui, Jian; Feng, Tanglue; Du, Xiaohang; Jin, Gan; Liu, Fangyuan; Ji, Tianjiao; Li, Fenghong; Zhang, Hao; Yang, Bai

    2017-09-20

    Aqueous-processed nanocrystal solar cells have attracted increasing attention due to the advantage of its environmentally friendly nature, which provides a promising approach for large-scale production. The urgent affair is boosting the power conversion efficiency (PCE) for further commercial applications. The low PCE is mainly attributed to the imperfect device structure, which leads to abundant nonradiative recombination at the interfaces. In this work, an environmentally friendly and efficient method is developed to improve the performance of aqueous-processed CdTe nanocrystal solar cells. Polymer/CdTe planar heterojunction solar cells (PHSCs) with optimized band alignment are constructed, which results in reduced interfacial charge recombination, enhanced carrier collection efficiency and built-in field. Finally, a champion PCE of 5.9%, which is a record for aqueous-processed solar cells based on CdTe nanocrystals, is achieved after optimizing the photovoltaic device.

  5. Investigation of field-dependent charge carrier generation and recombination in polymer based solar cells by transient extraction currents

    Energy Technology Data Exchange (ETDEWEB)

    Kniepert, Juliane; Blakesley, James; Neher, Dieter [University of Potsdam (Germany)

    2011-07-01

    There is an ongoing discussion as to whether photoinduced charge transfer in P3HT:PCBM solar cells leads to fully separated electrons and holes, independent of an electric field, or Coulombically bound interfacial charge pairs. While recent studies by R.A. Marsh et al. with transient absorption spectroscopy gave clear evidence for the formation and field-induced dissociation of bound polaron pairs, measurements by I.A. Howard et al. were in favour of hot exciton dissociation. Here, we present the results of bias-dependent Time Delayed Collection Field (TDCF) measurements to access directly the density of free charge carriers in P3HT:PCBM blends coated from dichlorobenzene. Solvent annealing was applied to yield a phase-separated morphology and the corresponding solar cells exhibit high values for the external quantum efficiency and fill factor. Our setup allowed us to follow the generation and recombination of photogenerated charges with a so far unattained time resolution of 40 ns. Our experiments show that the number of collected carriers is independent of the applied bias during pulsed illumination implying that extractable carriers in P3HT:PCBM blends are not generated by the field-assisted separation of bound polaron pairs. In addition, our experiments support the view that bimolecular recombination of free carriers is strongly suppressed in phase-separated P3HT:PBCM blends.

  6. Light-induced electron paramagnetic resonance evidence of charge transfer in electrospun fibers containing conjugated polymer/fullerene and conjugated polymer/fullerene/carbon nanotube blends

    Science.gov (United States)

    Shames, Alexander I.; Bounioux, Céline; Katz, Eugene A.; Yerushalmi-Rozen, Rachel; Zussman, Eyal

    2012-03-01

    Electrospun sub-micron fibers containing conjugated polymer (poly(3-hexylthiophene), P3HT) with a fullerene derivative, phenyl-C61-butyric acid methylester (PCBM) or a mixture of PCBM and single-walled carbon nanotubes (SWCNTs) were studied by light-induced electron paramagnetic resonance spectroscopy. The results provide experimental evidence of electron transfer between PCBM and P3HT components in both fiber systems and suggest that the presence of a dispersing block-copolymer, which acts via physical adsorption onto the PCBM and SWCNT moieties, does not prevent electron transfer at the P3HT-PCBM interface. These findings suggest a research perspective towards utilization of fibers of functional nanocomposites in fiber-based organic optoelectronic and photovoltaic devices. The latter can be developed in the textile-type large area photovoltaics or individual fiber-based solar cells that will broaden energy applications from macro-power tools to micro-nanoscale power conversion devices and smart textiles.

  7. Fine-tuning of charge-conversion polymer structure for efficient endosomal escape of siRNA-loaded calcium phosphate hybrid micelles.

    Science.gov (United States)

    Maeda, Yoshinori; Pittella, Frederico; Nomoto, Takahiro; Takemoto, Hiroyasu; Nishiyama, Nobuhiro; Miyata, Kanjiro; Kataoka, Kazunori

    2014-07-01

    For efficient delivery of siRNA into the cytoplasm, a smart block copolymer of poly(ethylene glycol) and charge-conversion polymer (PEG-CCP) is developed by introducing 2-propionic-3-methylmaleic (PMM) amide as an anionic protective group into side chains of an endosome-disrupting cationic polyaspartamide derivative. The PMM amide moiety is highly susceptible to acid hydrolysis, generating the parent cationic polyaspartamide derivative at endosomal acidic pH 5.5 more rapidly than a previously synthesized cis-aconitic (ACO) amide control. The PMM-based polymer is successfully integrated into a calcium phosphate (CaP) nanoparticle with siRNA, constructing PEGylated hybrid micelles (PMM micelles) having a sub-100 nm size at extracellular neutral pH 7.4. Ultimately, PMM micelles achieve the significantly higher gene silencing efficiency in cultured cancer cells, compared to ACO control micelles, probably due to the efficient endosomal escape of the PMM micelles. Thus, it is demonstrated that fine-tuning of acid-labile structures in CCP improves the delivery performance of siRNA-loaded nanocarriers.

  8. Calculating the binding free energies of charged species based on explicit-solvent simulations employing lattice-sum methods: An accurate correction scheme for electrostatic finite-size effects

    Energy Technology Data Exchange (ETDEWEB)

    Rocklin, Gabriel J. [Department of Pharmaceutical Chemistry, University of California San Francisco, 1700 4th St., San Francisco, California 94143-2550, USA and Biophysics Graduate Program, University of California San Francisco, 1700 4th St., San Francisco, California 94143-2550 (United States); Mobley, David L. [Departments of Pharmaceutical Sciences and Chemistry, University of California Irvine, 147 Bison Modular, Building 515, Irvine, California 92697-0001, USA and Department of Chemistry, University of New Orleans, 2000 Lakeshore Drive, New Orleans, Louisiana 70148 (United States); Dill, Ken A. [Laufer Center for Physical and Quantitative Biology, 5252 Stony Brook University, Stony Brook, New York 11794-0001 (United States); Hünenberger, Philippe H., E-mail: phil@igc.phys.chem.ethz.ch [Laboratory of Physical Chemistry, Swiss Federal Institute of Technology, ETH, 8093 Zürich (Switzerland)

    2013-11-14

    The calculation of a protein-ligand binding free energy based on molecular dynamics (MD) simulations generally relies on a thermodynamic cycle in which the ligand is alchemically inserted into the system, both in the solvated protein and free in solution. The corresponding ligand-insertion free energies are typically calculated in nanoscale computational boxes simulated under periodic boundary conditions and considering electrostatic interactions defined by a periodic lattice-sum. This is distinct from the ideal bulk situation of a system of macroscopic size simulated under non-periodic boundary conditions with Coulombic electrostatic interactions. This discrepancy results in finite-size effects, which affect primarily the charging component of the insertion free energy, are dependent on the box size, and can be large when the ligand bears a net charge, especially if the protein is charged as well. This article investigates finite-size effects on calculated charging free energies using as a test case the binding of the ligand 2-amino-5-methylthiazole (net charge +1 e) to a mutant form of yeast cytochrome c peroxidase in water. Considering different charge isoforms of the protein (net charges −5, 0, +3, or +9 e), either in the absence or the presence of neutralizing counter-ions, and sizes of the cubic computational box (edges ranging from 7.42 to 11.02 nm), the potentially large magnitude of finite-size effects on the raw charging free energies (up to 17.1 kJ mol{sup −1}) is demonstrated. Two correction schemes are then proposed to eliminate these effects, a numerical and an analytical one. Both schemes are based on a continuum-electrostatics analysis and require performing Poisson-Boltzmann (PB) calculations on the protein-ligand system. While the numerical scheme requires PB calculations under both non-periodic and periodic boundary conditions, the latter at the box size considered in the MD simulations, the analytical scheme only requires three non

  9. Effects of compatibility of polymer binders with solvate ionic liquid electrolytes on discharge and charge reactions of lithium-sulfur batteries

    Science.gov (United States)

    Nakazawa, Toshitada; Ikoma, Ai; Kido, Ryosuke; Ueno, Kazuhide; Dokko, Kaoru; Watanabe, Masayoshi

    2016-03-01

    Electrochemical reactions in Li-S cells with a solvate ionic liquid (SIL) electrolyte composed of tetraglyme (G4) and Li[TFSA] (TFSA: bis(trifluoromethanesulfonyl)amide) are studied. The sulfur cathode (S cathode) comprises sulfur, carbon powder, and a polymer binder. Poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA-x) with different degrees of saponification (x%) are used as binders to prepare the composite cathodes. For the Li-S cell containing PEO binder, lithium polysulfides (Li2Sm, 2 ≤ m ≤ 8), reaction intermediates of the S cathode, dissolve into the electrolyte, and Li2Sm acts as a redox shuttle in the Li-S cell. In contrast, in the Li-S cell with PVA-x binder, the dissolution of Li2Sm is suppressed, leading to high columbic efficiencies during charge-discharge cycles. The compatibility of the PVA-x binder with the SIL electrolyte changes depending on the degree of saponification. Decreasing the degree of saponification leads to increased electrolyte uptake by the PVA-x binder, increasing the charge and discharge capacities of Li-S cell. The rate capability of Li-S cell is also enhanced by the partial swelling of the PVA-x binder. The enhanced performance of Li-S cell containing PVA-x is attributed to the lowering of resistance of Li+ ion transport in the composite cathode.

  10. Optimization of charge carrier transport balance for performance improvement of PDPP3T-based polymer solar cells prepared using a hot solution.

    Science.gov (United States)

    Wang, Jian; Zhang, Fujun; Zhang, Miao; Wang, Wenbin; An, Qiaoshi; Li, Lingliang; Sun, Qianqian; Tang, Weihua; Zhang, Jian

    2015-04-21

    Polymer solar cells (PSCs), with poly(diketopyrrolopyrrole-terthiophene) (PDPP3T):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the active layers, were fabricated using solutions of different temperatures. The best power conversion efficiency (PCE) of the PSCs prepared using a hot solution was about 6.22%, which is better than 5.54% for PSCs prepared using cool (room temperature) solutions and 5.85% for PSCs prepared using cool solutions with a 1,8-diiodooctane (DIO) solvent additive. The underlying reasons for the improved PCE of the PSCs prepared using a hot solution could be attributed to the more dispersive donor and acceptor distribution in the active layer, resulting in a better bi-continuous interpenetrating network for exciton dissociation and charge carrier transport. An enhanced and more balanced charge carrier transport in the active layer is obtained for the PSCs prepared using a hot solution, which can be determined from the J-V curves of the related hole-only and electron-only devices.

  11. Topological Lattice Actions

    CERN Document Server

    Bietenholz, W; Pepe, M; Wiese, U -J

    2010-01-01

    We consider lattice field theories with topological actions, which are invariant against small deformations of the fields. Some of these actions have infinite barriers separating different topological sectors. Topological actions do not have the correct classical continuum limit and they cannot be treated using perturbation theory, but they still yield the correct quantum continuum limit. To show this, we present analytic studies of the 1-d O(2) and O(3) model, as well as Monte Carlo simulations of the 2-d O(3) model using topological lattice actions. Some topological actions obey and others violate a lattice Schwarz inequality between the action and the topological charge $Q$. Irrespective of this, in the 2-d O(3) model the topological susceptibility $\\chi_t = \\l/V$ is logarithmically divergent in the continuum limit. Still, at non-zero distance the correlator of the topological charge density has a finite continuum limit which is consistent with analytic predictions. Our study shows explicitly that some cla...

  12. Lattice theory

    CERN Document Server

    Donnellan, Thomas; Maxwell, E A; Plumpton, C

    1968-01-01

    Lattice Theory presents an elementary account of a significant branch of contemporary mathematics concerning lattice theory. This book discusses the unusual features, which include the presentation and exploitation of partitions of a finite set. Organized into six chapters, this book begins with an overview of the concept of several topics, including sets in general, the relations and operations, the relation of equivalence, and the relation of congruence. This text then defines the relation of partial order and then partially ordered sets, including chains. Other chapters examine the properti

  13. A three-dimensional pore-scale model of the cathode electrode in polymer-electrolyte membrane fuel cell by lattice Boltzmann method

    Science.gov (United States)

    Molaeimanesh, G. R.; Akbari, M. H.

    2014-07-01

    High power density, low operation temperature, high efficiency and low emissions have granted proton exchange membrane (PEM) fuel cells the most promising future among all types of fuel cells. The porous electrodes of PEM fuel cells have a complicated, non-homogeneous, anisotropic microstructure. Therefore, pore-scale modeling techniques such as lattice Boltzmann method, which can capture non-homogeneous and anisotropic microstructures, have recently gained a great attention. In the present study, a three-dimensional lattice Boltzmann model of a PEM fuel cell cathode electrode is proposed in which electrochemical reaction on the catalyst layer and microstructure of GDL are taken into account. The model enables us to simulate single-phase, multi-species reactive flow in a heterogeneous, anisotropic gas diffusion layer through an active approach. To show the capability of the proposed model, reactive flow in three reconstructed GDLs with different anisotropic characteristics is simulated to investigate the effects of GDL microstructure on species and current density distributions. The results demonstrate that when carbon fibers are more likely oriented normal to the catalyst layer, species density distribution is thicker and more disturbed. Current density also experiences a larger variation on the catalyst layer in such a case.

  14. Isolation and fractionation of CHO chromosomes in aqueous two phase systems using charged polymers and base specific macroligands.

    Science.gov (United States)

    Klaar, J; Kula, M R

    1986-02-01

    Chromosomes were isolated in a preparative scale by synchronisation of CHO cells with a double Thymidine block followed by an arrest in the metaphase by addition of Colcemid. Under proper cultivation conditions a mitotic index of 77% total cells could be routinely achieved. Bulk chromosome preparations free of nuclei and other subcellular particles have been obtained by low speed centrifugation followed by a 60 transfer countercurrent distribution using aqueous two phase systems composed of polyethylenglycol and dextran. The partition of CHO chromosomes previously purified in aqueous two phase systems were studied further to develop a protocol for the separation and isolation of individual chromosomes. Partition experiments with chromosomes changing the electrostatic phase potential by addition of charged PEG-derivatives suggest the existence of relatively highly charged chromosome groups. Most promising results with regard to separation were obtained using two PEG-derivatives, which interact specifically with the bases in DNA. For this affinity partitioning a GC- and AT-specific macroligand were employed. Comparing CCD's using each of these ligands information on the GC and AT content of exposed DNA in the chromosomes groups could be derived, demonstrating that specific sequences of DNA are accessible at the surface of metaphase chromosomes.

  15. Understanding Parton Distributions from Lattice QCD

    OpenAIRE

    Renner, Dru B.

    2005-01-01

    I examine the past lattice QCD calculations of three representative observables, the transverse quark distribution, momentum fraction, and axial charge, and emphasize the prospects for not only quantitative comparison with experiment but also qualitative understanding of QCD.

  16. Kaon fluctuations from lattice QCD

    CERN Document Server

    Noronha-Hostler, Jacquelyn; Gunther, Jana; Parotto, Paolo; Pasztor, Attila; Vazquez, Israel Portillo; Ratti, Claudia

    2016-01-01

    We show that it is possible to isolate a set of kaon fluctuations in lattice QCD. By means of the Hadron Resonance Gas (HRG) model, we calculate the actual kaon second-to-first fluctuation ratio, which receives contribution from primordial kaons and resonance decays, and show that it is very close to the one obtained for primordial kaons in the Boltzmann approximation. The latter only involves the strangeness and electric charge chemical potentials, which are functions of $T$ and $\\mu_B$ due to the experimental constraint on strangeness and electric charge, and can therefore be calculated on the lattice. This provides an unambiguous method to extract the kaon freeze-out temperature, by comparing the lattice results to the experimental values for the corresponding fluctuations.

  17. Hadron Structure on the Lattice

    Science.gov (United States)

    Can, K. U.; Kusno, A.; Mastropas, E. V.; Zanotti, J. M.

    The aim of these lectures will be to provide an introduction to some of the concepts needed to study the structure of hadrons on the lattice. Topics covered include the electromagnetic form factors of the nucleon and pion, the nucleon's axial charge and moments of parton and generalised parton distribution functions. These are placed in a phenomenological context by describing how they can lead to insights into the distribution of charge, spin and momentum amongst a hadron's partonic constituents. We discuss the techniques required for extracting the relevant matrix elements from lattice simulations and draw attention to potential sources of systematic error. Examples of recent lattice results are presented and are compared with results from both experiment and theoretical models.

  18. Nucleon structure using lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Alexandrou, C.; Kallidonis, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Constantinou, M.; Hatziyiannakou, K. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Drach, V. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Jansen, K. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Koutsou, G.; Vaquero, A. [The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Leontiou, T. [Frederick Univ, Nicosia (Cyprus). General Dept.

    2013-03-15

    A review of recent nucleon structure calculations within lattice QCD is presented. The nucleon excited states, the axial charge, the isovector momentum fraction and helicity distribution are discussed, assessing the methods applied for their study, including approaches to evaluate the disconnected contributions. Results on the spin carried by the quarks in the nucleon are also presented.

  19. Topology of four-dimensional lattice gauge fields

    Science.gov (United States)

    Panagiotakopoulos, C.

    1985-08-01

    An extremely careful implementation of Woit's definition of the topological charge for SU(2) lattice gauge fields reveals a scaling violation by the topological susceptibility in the region 2.1Luscher's charge at weak enough coupling.

  20. Discrimination between spin-dependent charge transport and spin-dependent recombination in π-conjugated polymers by correlated current and electroluminescence-detected magnetic resonance

    Science.gov (United States)

    Kavand, Marzieh; Baird, Douglas; van Schooten, Kipp; Malissa, Hans; Lupton, John M.; Boehme, Christoph

    2016-08-01

    Spin-dependent processes play a crucial role in organic electronic devices. Spin coherence can give rise to spin mixing due to a number of processes such as hyperfine coupling, and leads to a range of magnetic field effects. However, it is not straightforward to differentiate between pure single-carrier spin-dependent transport processes which control the current and therefore the electroluminescence, and spin-dependent electron-hole recombination which determines the electroluminescence yield and in turn modulates the current. We therefore investigate the correlation between the dynamics of spin-dependent electric current and spin-dependent electroluminescence in two derivatives of the conjugated polymer poly(phenylene-vinylene) using simultaneously measured pulsed electrically detected (pEDMR) and optically detected (pODMR) magnetic resonance spectroscopy. This experimental approach requires careful analysis of the transient response functions under optical and electrical detection. At room temperature and under bipolar charge-carrier injection conditions, a correlation of the pEDMR and the pODMR signals is observed, consistent with the hypothesis that the recombination currents involve spin-dependent electronic transitions. This observation is inconsistent with the hypothesis that these signals are caused by spin-dependent charge-carrier transport. These results therefore provide no evidence that supports earlier claims that spin-dependent transport plays a role for room-temperature magnetoresistance effects. At low temperatures, however, the correlation between pEDMR and pODMR is weakened, demonstrating that more than one spin-dependent process influences the optoelectronic materials' properties. This conclusion is consistent with prior studies of half-field resonances that were attributed to spin-dependent triplet exciton recombination, which becomes significant at low temperatures when the triplet lifetime increases.

  1. Phase structure of lattice N=4 super Yang-Mills

    DEFF Research Database (Denmark)

    Catterall, Simon; Damgaard, Poul H.; DeGrand, Thomas;

    2012-01-01

    We make a first study of the phase diagram of four-dimensional N = 4 super Yang-Mills theory regulated on a space-time lattice. The lattice formulation we employ is both gauge invariant and retains at all lattice spacings one exactly preserved supersymmetry charge. Our numerical results are consi...

  2. Lattice QCD on fine lattices

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Stefan [DESY (Germany). Neumann Inst. for Computing

    2016-11-01

    These configurations are currently in use in many on-going projects carried out by researchers throughout Europe. In particular this data will serve as an essential input into the computation of the coupling constant of QCD, where some of the simulations are still on-going. But also projects computing the masses of hadrons and investigating their structure are underway as well as activities in the physics of heavy quarks. As this initial project of gauge field generation has been successful, it is worthwhile to extend the currently available ensembles with further points in parameter space. These will allow to further study and control systematic effects like the ones introduced by the finite volume, the non-physical quark masses and the finite lattice spacing. In particular certain compromises have still been made in the region where pion masses and lattice spacing are both small. This is because physical pion masses require larger lattices to keep the effects of the finite volume under control. At light pion masses, a precise control of the continuum extrapolation is therefore difficult, but certainly a main goal of future simulations. To reach this goal, algorithmic developments as well as faster hardware will be needed.

  3. Chiral Fermions on the Lattice

    CERN Document Server

    Bietenholz, Wolfgang

    2010-01-01

    In the last century the non-perturbative regularization of chiral fermions was a long-standing problem. We review how this problem was finally overcome by the formulation of a modified but exact form of chiral symmetry on the lattice. This also provides a sound definition of the topological charge of lattice gauge configurations. We illustrate a variety of applications to QCD in the p-, the epsilon- and the delta-regime, where simulation results can now be related to Random Matrix Theory and Chiral Perturbation Theory. The latter contains Low Energy Constants as free parameters, and we comment on their evaluation from first principles of QCD.

  4. Advances in Lattice Quantum Chromodynamics

    Science.gov (United States)

    McGlynn, Greg

    In this thesis we make four contributions to the state of the art in numerical lattice simulations of quantum chromodynamics (QCD). First, we present the most detailed investigation yet of the autocorrelations of topological observations in hybrid Monte Carlo simulations of QCD and of the effects of the boundary conditions on these autocorrelations. This results in a numerical criterion for deciding when open boundary conditions are useful for reducing these autocorrelations, which are a major barrier to reliable calculations at fine lattice spacings. Second, we develop a dislocation-enhancing determinant, and demonstrate that it reduces the autocorrelation time of the topological charge. This alleviates problems with slow topological tunneling at fine lattice spacings, enabling simulations on fine lattices to be completed with much less computational effort. Third, we show how to apply the recently developed zMobius technique to hybrid Monte Carlo evolutions with domain wall fermions, achieving nearly a factor of two speedup in the light quark determinant, the single most expensive part of the calculation. The dislocation-enhancing determinant and the zMobius technique have enabled us to begin simulations of fine ensembles with four flavors of dynamical domain wall quarks. Finally, we show how to include the previously-neglected G1 operator in nonperturbative renormalization of the DeltaS = 1 effective weak Hamiltonian on the lattice. This removes an important systematic error in lattice calculations of weak matrix elements, in particular the important K → pipi decay.

  5. Charge mediation by ruthenium poly(pyridine) complexes in 'second-generation' glucose biosensors based on carboxymethylated beta-cyclodextrin polymer membranes.

    Science.gov (United States)

    Kosela, Edyta; Elzanowska, Hanna; Kutner, Wlodzimierz

    2002-04-01

    Four different poly(pyridine) complexes of ruthenium, viz. Ru(II)(trpy)(phen)(OH(2))](2+) (1), trans-[Ru(III)(2,2'bpy)(2)(OH(2))(OH)](2+) (2), [(2,2'bpy)(2)(OH)Ru(III)ORu(III)(OH)(2,2'bpy)(2)](4+) (3), and [Ru(II)(4,4'bpy)(NH(3))(5)](2+) (4) (2,2'bpy=2,2'-bipyridine, 4,4'bpy=4,4'-bipyridine, trpy=2,2',2"-terpyridine, phen=1,10-phenanthroline), were tested as non-physiological charge mediators of 'second-generation' glucose biosensors. The membranes for these biosensors were prepared by casting anionic carboxymethylated beta-cyclodextrin polymer films (beta-CDPA) directly onto the Pt or glassy carbon (GC) disk electrodes. Simultaneously, glucose oxidase (GOD) was immobilized in the films by covalent bonding and the Ru complexes were incorporated both by inclusion in the beta-CD molecular cavities and by ion exchange at the fixed carboxymethyl cation-exchange sites. The leakage of the mediator from the polymer has been minimized by adopting a suitable pre-treatment procedure. The biosensors catalytic activities increased in the order 1inclusion complex with beta-CD, the biosensor sensitivity was the highest and equal to 7.2 micro A mM(-1) cm(-2), detectability was as low as 1 mM, but the linear concentration range was limited only to 4 mM. In contrast, for complexes 2 and 3 the sensitivity was 0.4 and 3.2 micro A mM(-1) cm(-2), while the linear concentration range extended up to at least 24 and 14 mM glucose, respectively. Even though some common interfering substances, such as ascorbate, paracetamol or urea, are oxidized at potentials close to those of the Ru complex redox couples, their electro-oxidation currents at physiological concentrations are insignificant compared to those due to the biocatalytic oxidation of glucose. The biosensor response to glucose is reversible as demonstrated by the inhibition of GOD activity by Cu(II). That is, the Cu(II) concentration required to inhibit by half the response to glucose of the biosensor containing complex 2 was 1.0 m

  6. Dual Lattice of ℤ-module Lattice

    Directory of Open Access Journals (Sweden)

    Futa Yuichi

    2017-07-01

    Full Text Available In this article, we formalize in Mizar [5] the definition of dual lattice and their properties. We formally prove that a set of all dual vectors in a rational lattice has the construction of a lattice. We show that a dual basis can be calculated by elements of an inverse of the Gram Matrix. We also formalize a summation of inner products and their properties. Lattice of ℤ-module is necessary for lattice problems, LLL(Lenstra, Lenstra and Lovász base reduction algorithm and cryptographic systems with lattice [20], [10] and [19].

  7. Tunable nanoparticle arrays at charged interfaces.

    Science.gov (United States)

    Srivastava, Sunita; Nykypanchuk, Dmytro; Fukuto, Masafumi; Gang, Oleg

    2014-10-28

    Structurally tunable two-dimensional (2D) arrays of nanoscale objects are important for modulating functional responses of thin films. We demonstrate that such tunable and ordered nanoparticles (NP) arrays can be assembled at charged air-water interfaces from nanoparticles coated with polyelectrolyte chains, DNA. The electrostatic attraction between the negatively charged nonhybridizing DNA-coated gold NPs and a positively charged lipid layer at the interface facilitates the formation of a 2D hexagonally closed packed (HCP) nanoparticle lattice. We observed about 4-fold change of the monolayer nanoparticle density by varying the ionic strength of the subphase. The tunable NP arrays retain their structure reasonably well when transferred to a solid support. The influence of particle's DNA corona and lipid layer composition on the salt-induced in-plane and normal structural evolution of NP arrays was studied in detail using a combination of synchrotron-based in situ surface scattering methods, grazing incidence X-ray scattering (GISAXS), and X-ray reflectivity (XRR). Comparative analysis of the interparticle distances as a function of ionic strength reveals the difference between the studied 2D nanoparticle arrays and analogous bulk polyelectrolyte star polymers systems, typically described by Daoud-Cotton model and power law scaling. The observed behavior of the 2D nanoparticle array manifests a nonuniform deformation of the nanoparticle DNA corona due to its electrostatically induced confinement at the lipid interface. The present study provides insight on the interfacial properties of the NPs coated with charged soft shells.

  8. Invariant patterns in crystal lattices: Implications for protein folding algorithms

    Energy Technology Data Exchange (ETDEWEB)

    HART,WILLIAM E.; ISTRAIL,SORIN

    2000-06-01

    Crystal lattices are infinite periodic graphs that occur naturally in a variety of geometries and which are of fundamental importance in polymer science. Discrete models of protein folding use crystal lattices to define the space of protein conformations. Because various crystal lattices provide discretizations of the same physical phenomenon, it is reasonable to expect that there will exist invariants across lattices related to fundamental properties of the protein folding process. This paper considers whether performance-guaranteed approximability is such an invariant for HP lattice models. The authors define a master approximation algorithm that has provable performance guarantees provided that a specific sublattice exists within a given lattice. They describe a broad class of crystal lattices that are approximable, which further suggests that approximability is a general property of HP lattice models.

  9. Lattice Stern-Gerlach experiment

    CERN Document Server

    Luschevskaya, E V; Teryaev, O V

    2016-01-01

    We investigate the dependence of ground state energies of charged vector $\\rho$ and $K^{*}$ mesons on the value of magnetic field in the $SU(3)$ lattice gauge theory. It has been shown that the energy of a vector particle strongly depends on its spin projection on the field axis, and the magnetic dypole polarizability and hyperpolarizabilities give a large contribution to the meson energy at large fields. We calculate the g-factor of $\\rho^{\\pm}$ and $K^{*\\pm}$ mesons. Tensor of the dypole magnetic polarizability of the charged $\\rho$ meson at rest has been found.

  10. Harmonic Lattice Dynamics of Germanium

    Energy Technology Data Exchange (ETDEWEB)

    Nelin, G.

    1974-07-01

    The phonon dispersion relations of the DELTA-, LAMBDA-, and SIGMA-directions of germanium at 80 K are analysed in terms of current harmonic lattice dynamical models. On the basis of this experience, a new model is proposed which gives a unified account of the strong points of the previous models. The principal elements of the presented theory are quasiparticle bond charges combined with a valence force field.

  11. Evidence for a Lattice Weak Gravity Conjecture

    CERN Document Server

    Heidenreich, Ben; Rudelius, Tom

    2016-01-01

    The Weak Gravity Conjecture postulates the existence of superextremal charged particles, i.e. those with mass smaller than or equal to their charge in Planck units. We present further evidence for our recent observation that in known examples a much stronger statement is true: an infinite tower of superextremal particles of different charges exists. We show that effective Kaluza-Klein field theories and perturbative string vacua respect the Sublattice Weak Gravity Conjecture, namely that a finite index sublattice of the full charge lattice exists with a superextremal particle at each site. In perturbative string theory we show that this follows from modular invariance. However, we present counterexamples to the stronger possibility that a superextremal state exists at every lattice site, including an example in which the lightest charged state is subextremal. The Sublattice Weak Gravity Conjecture has many implications both for abstract theories of quantum gravity and for real-world physics. For instance, it ...

  12. Nonlinear electrodynamics in cytoskeletal protein lattices

    Energy Technology Data Exchange (ETDEWEB)

    Hameroff, S.R.; Smith, S.A.; Watt, R.C.

    1983-01-01

    Cytoskeletal lattice proteins including microtubules are particularly involved in dynamic regulation of intracellular movements and activities. This paper considers possibilities and implications of biological information processing due to coupling of Davydov solitons, Frohlich coherent oscillations and other nonlinear electrodynamic phenomena to conformational states of the grid-like polymer subunits of cytoskeletal microtubules. 39 references.

  13. APS-U LATTICE DESIGN FOR OFF-AXIS ACCUMULATION

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yipeng; Borland, M.; Lindberg, R.; Sajaev, V.

    2017-06-25

    A 67-pm hybrid-seven-bend achromat (H7BA) lattice is being proposed for a future Advanced Photon Source (APS) multi-bend-achromat (MBA) upgrade project. This lattice design pushes for smaller emittance and requires use of a swap-out (on-axis) injection scheme due to limited dynamic acceptance. Alternate lattice design work has also been performed for the APS upgrade to achieve better beam dynamics performance than the nominal APS MBA lattice, in order to allow off-axis accumulation. Two such alternate H7BA lattice designs, which target a still-low emittance of 90 pm, are discussed in detail in this paper. Although the single-particle-dynamics performance is good, simulations of collective effects indicate that surprising difficulty would be expected accumulating high single-bunch charge in this lattice. The brightness of the 90-pm lattice is also a factor of two lower than the 67-pm H7BA lattice.

  14. Free µ-Lattices

    DEFF Research Database (Denmark)

    Santocanale, Luigi

    2002-01-01

    A μ-lattice is a lattice with the property that every unary polynomial has both a least and a greatest fix-point. In this paper we define the quasivariety of μ-lattices and, for a given partially ordered set P, we construct a μ-lattice JP whose elements are equivalence classes of games in a preor...

  15. U-Duality and the Leech Lattice

    CERN Document Server

    Rios, Michael

    2013-01-01

    It has recently been shown that the full automorphism group of the Leech lattice, Conway's group Co_0, can be generated by 3 x 3 matrices over the octonions. We show such matrices are of type F_4 in E_{6(-26)}, the U-duality group for N=2, D=5 exceptional magic supergravity. By mapping points of the Leech lattice to black hole charge vectors, it is seen Conway's group Co_0 is generated by U-duality transformations acting as rotations in the charge space for BPS black holes.

  16. Fractal lattice of gelatin nanoglobules

    Science.gov (United States)

    Novikov, D. V.; Krasovskii, A. N.

    2012-11-01

    The globular structure of polymer coatings on a glass, which were obtained from micellar solutions of gelatin in the isooctane-water-sodium (bis-2-ethylhexyl) sulfosuccinate system, has been studied using electron microscopy. It has been shown that an increase in the average globule size is accompanied by the formation of a fractal lattice of nanoglobules and a periodic physical network of macromolecules in the coating. The stability of such system of the "liquid-in-a-solid" type is limited by the destruction of globules and the formation of a homogeneous network structure of the coating.

  17. Electrochemical characterization of surface-bound redox polymers derived from 1,1'-bis(((3-(triethoxysilyl)propyl)amino)carbonyl)cobaltocenium: charge transport, anion binding, and use in photoelectrochemical hydrogen generation

    Energy Technology Data Exchange (ETDEWEB)

    Simon, R.A.; Mallouk, T.E.; Daube, K.A.; Wrighton, M.S.

    1985-09-25

    This paper describes the behavior of electrode-bound redox material derived from the hydrolysis of the -Si(OEt)/sub 3/ groups of 1,1'-bis(((3-(triethoxysilyl)propyl)amino)carbonyl)cobaltocenium (I). Surfaces of the conventional electrodes SnO/sub 2/ and Pt derivatized with I have a reversible electrochemical response in H/sub 2/O/electrolyte; the E/sup 0/' is pH independent at -0.62 V vs. SCE. The photoelectrochemical behavior of p-type Si photocathodes derivatized with I reveals that the photoreduction of the cobaltocenium derivative can be effected at an electrode potential approx. 500 mV more positive than on metallic electrodes, consistent with the known behavior of p-type Si photocathodes. When polymer from I is deposited on p-type Si and subsequently coated with a small amount of Rh or Pd (approx. 10/sup -7/ mol/cm/sup 2/), the photoelectrochemical generation of H/sub 2/ is possible with 632.8-nm (approx. 15 mW/cm/sup 2/) radiation and efficiencies in the vicinity of 2%. The polymer derived from I is more optically transparent and more durable at negative potentials than redox polymers derived from vilogen monomers. Potential-step measurements and steady-state-current measurements for mediated redox processes show that the charge-transport rate for the polymer derived from I is about the same as for polymers from viologen monomers. 32 references, 8 figures.

  18. Cold atoms in a rotating optical lattice

    Science.gov (United States)

    Foot, Christopher J.

    2009-05-01

    We have demonstrated a novel experimental arrangement which can rotate a two-dimensional optical lattice at frequencies up to several kilohertz. Our arrangement also allows the periodicity of the optical lattice to be varied dynamically, producing a 2D ``accordion lattice'' [1]. The angles of the laser beams are controlled by acousto-optic deflectors and this allows smooth changes with little heating of the trapped cold (rubidium) atoms. We have loaded a BEC into lattices with periodicities ranging from 1.8μm to 18μm, observing the collapse and revival of the diffraction orders of the condensate over a large range of lattice parameters as recently reported by a group in NIST [2]. We have also imaged atoms in situ in a 2D lattice over a range of lattice periodicities. Ultracold atoms in a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, i.e. the Hamiltonian of the atoms in the rotating frame resembles that of a charged particle in a strong magnetic field. In the future, we plan to use this to investigate a range of phenomena such as the analogue of the fractional quantum Hall effect. [4pt] [1] R. A. Williams, J. D. Pillet, S. Al-Assam, B. Fletcher, M. Shotter, and C. J. Foot, ``Dynamic optical lattices: two-dimensional rotating and accordion lattices for ultracold atoms,'' Opt. Express 16, 16977-16983 (2008) [0pt] [2] J. H. Huckans, I. B. Spielman, B. Laburthe Tolra, W. D. Phillips, and J. V. Porto, Quantum and Classical Dynamics of a BEC in a Large-Period Optical Lattice, arXiv:0901.1386v1

  19. Manipulation and quantification of microtubule lattice integrity

    Directory of Open Access Journals (Sweden)

    Taylor A. Reid

    2017-08-01

    Full Text Available Microtubules are structural polymers that participate in a wide range of cellular functions. The addition and loss of tubulin subunits allows the microtubule to grow and shorten, as well as to develop and repair defects and gaps in its cylindrical lattice. These lattice defects act to modulate the interactions of microtubules with molecular motors and other microtubule-associated proteins. Therefore, tools to control and measure microtubule lattice structure will be invaluable for developing a quantitative understanding of how the structural state of the microtubule lattice may regulate its interactions with other proteins. In this work, we manipulated the lattice integrity of in vitro microtubules to create pools of microtubules with common nucleotide states, but with variations in structural states. We then developed a series of novel semi-automated analysis tools for both fluorescence and electron microscopy experiments to quantify the type and severity of alterations in microtubule lattice integrity. These techniques will enable new investigations that explore the role of microtubule lattice structure in interactions with microtubule-associated proteins.

  20. Spacecraft dielectric material properties and spacecraft charging

    Science.gov (United States)

    Frederickson, A. R.; Wall, J. A.; Cotts, D. B.; Bouquet, F. L.

    1986-01-01

    The physics of spacecraft charging is reviewed, and criteria for selecting and testing semiinsulating polymers (SIPs) to avoid charging are discussed and illustrated. Chapters are devoted to the required properties of dielectric materials, the charging process, discharge-pulse phenomena, design for minimum pulse size, design to prevent pulses, conduction in polymers, evaluation of SIPs that might prevent spacecraft charging, and the general response of dielectrics to space radiation. SIPs characterized include polyimides, fluorocarbons, thermoplastic polyesters, poly(alkanes), vinyl polymers and acrylates, polymers containing phthalocyanine, polyacene quinones, coordination polymers containing metal ions, conjugated-backbone polymers, and 'metallic' conducting polymers. Tables summarizing the results of SIP radiation tests (such as those performed for the NASA Galileo Project) are included.

  1. Charge transport in polymeric transistors

    Directory of Open Access Journals (Sweden)

    Alberto Salleo

    2007-03-01

    Full Text Available Polymeric semiconductors have attracted much attention because of their possible use as active materials in printed electronics. Thin-film transistors (TFTs are a convenient tool for studying charge-transport physics in conjugated polymers. Two families of materials are reviewed here: fluorene copolymers and polythiophenes. Because charge transport is highly anisotropic in molecular conductors, the electrical properties of conjugated polymers are strongly dependent on microstructure. Molecular weight, polydispersity, and regioregularity all affect morphology and charge-transport in these materials. Charge transport models based on microstructure are instrumental in identifying the electrical bottlenecks in these materials.

  2. Self-consistent kinetic lattice Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Horsfield, A.; Dunham, S.; Fujitani, Hideaki

    1999-07-01

    The authors present a brief description of a formalism for modeling point defect diffusion in crystalline systems using a Monte Carlo technique. The main approximations required to construct a practical scheme are briefly discussed, with special emphasis on the proper treatment of charged dopants and defects. This is followed by tight binding calculations of the diffusion barrier heights for charged vacancies. Finally, an application of the kinetic lattice Monte Carlo method to vacancy diffusion is presented.

  3. Controllable conversion of quasi-freestanding polymer chains to graphene nanoribbons

    Science.gov (United States)

    Ma, Chuanxu; Xiao, Zhongcan; Zhang, Honghai; Liang, Liangbo; Huang, Jingsong; Lu, Wenchang; Sumpter, Bobby G.; Hong, Kunlun; Bernholc, J.; Li, An-Ping

    2017-03-01

    In the bottom-up synthesis of graphene nanoribbons (GNRs) from self-assembled linear polymer intermediates, surface-assisted cyclodehydrogenations usually take place on catalytic metal surfaces. Here we demonstrate the formation of GNRs from quasi-freestanding polymers assisted by hole injections from a scanning tunnelling microscope (STM) tip. While catalytic cyclodehydrogenations typically occur in a domino-like conversion process during the thermal annealing, the hole-injection-assisted reactions happen at selective molecular sites controlled by the STM tip. The charge injections lower the cyclodehydrogenation barrier in the catalyst-free formation of graphitic lattices, and the orbital symmetry conservation rules favour hole rather than electron injections for the GNR formation. The created polymer-GNR intraribbon heterostructures have a type-I energy level alignment and strongly localized interfacial states. This finding points to a new route towards controllable synthesis of freestanding graphitic layers, facilitating the design of on-surface reactions for GNR-based structures.

  4. Ion conducting interpenetrated lattices for lithium generators; Reseaux interpenetres conducteurs ioniques pour generateurs au lithium

    Energy Technology Data Exchange (ETDEWEB)

    Grosz, M.; Boileau, S. [College de France, 75 - Paris (France); Guegan, P.; Cheradame, H. [Centre National de la Recherche Scientifique (CNRS), 94 - Thiais (France). LPCB; Deshayes, A. [CNET, 92 - Issy-les-Moulineaux (France)

    1996-12-31

    Interpenetrated lattices (IPL) are combinations of reticulated polymers linked together by permanent crisscross. This structure is well-adapted to combined highly incompatible pairs of polymers. The in-situ sequential method has been applied successfully to the synthesis of ethylene poly-oxides / poly-siloxanes IPLs. The results concerning the preparation of such lattices and their behaviour as solid polymer electrolytes are presented in this paper. (J.S.) 24 refs.

  5. Lattice QCD on nonorientable manifolds

    Science.gov (United States)

    Mages, Simon; Tóth, Bálint C.; Borsányi, Szabolcs; Fodor, Zoltán; Katz, Sándor D.; Szabó, Kálmán K.

    2017-05-01

    A common problem in lattice QCD simulations on the torus is the extremely long autocorrelation time of the topological charge when one approaches the continuum limit. The reason is the suppressed tunneling between topological sectors. The problem can be circumvented by replacing the torus with a different manifold, so that the connectivity of the configuration space is changed. This can be achieved by using open boundary conditions on the fields, as proposed earlier. It has the side effect of breaking translational invariance strongly. Here we propose to use a nonorientable manifold and show how to define and simulate lattice QCD on it. We demonstrate in quenched simulations that this leads to a drastic reduction of the autocorrelation time. A feature of the new proposal is that translational invariance is preserved up to exponentially small corrections. A Dirac fermion on a nonorientable manifold poses a challenge to numerical simulations: the fermion determinant becomes complex. We propose two approaches to circumvent this problem.

  6. The Coulombic Lattice Potential of Ionic Compounds: The Cubic Perovskites.

    Science.gov (United States)

    Francisco, E.; And Others

    1988-01-01

    Presents coulombic models representing the particles of a system by point charges interacting through Coulomb's law to explain coulombic lattice potential. Uses rubidium manganese trifluoride as an example of cubic perovskite structure. Discusses the effects on cluster properties. (CW)

  7. Quasi-solid state polymer electrolytes for dye-sensitized solar cells. Effect of the electrolyte components variation on the triiodide ion diffusion properties and charge-transfer resistance at platinum electrode

    Energy Technology Data Exchange (ETDEWEB)

    Nazmutdinova, G.; Sensfuss, S.; Schroedner, M. [Thuringian Institute for Textile and Plastics Research, Breitscheidstrasse 97, 07407 Rudolstadt (Germany); Hinsch, A. [Fraunhofer Institute for Solar Energy Systems, Heidenhofstrasse 2, 79110 Freiburg (Germany); Sastrawan, R. [Freiburg Materials Research Center FMF, Stefan-Meier-Street 21, 79104 Freiburg (Germany); Gerhard, D.; Himmler, S.; Wasserscheid, P. [Friedrich-Alexander-University, Egerlandstrasse 3, 91058 Erlangen (Germany)

    2006-11-30

    Quasi-solid state polymer electrolytes have been prepared from poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) as gelator for 1-ethyl-3-methylimidazolium based ionic liquids (with anions like trifluoromethanesulfonate [EMIM][TfO], bis(trifluoromethanesulfonyl)imide [EMIM][Tf{sub 2}N]) and polyacrylonitrile (PAN) for gelation of 1-ethyl-3-methylimidazolium dicyanamide [EMIM][DCA] as well as I{sup -}/I{sub 3}{sup -} as the redox couple. All electrolytes exhibit high ionic conductivity in the range of 10{sup -3} S/cm. The effect of gelation, redox couple concentration, I{sup -}/I{sub 3}{sup -} ratio, choice of cations and additives on the triiodide diffusion and charge-transfer resistance of the platinum/electrolyte interface (R{sub ct}) were studied. The apparent diffusion coefficient of triiodide ion (D(I{sub 3}{sup -})) at various iodide/triiodide ratios in liquid and gelified electrolytes has been calculated from measurements of the diffusion limited current (I{sub lim}) in electrochemical cell resembling the set-up of a dye-sensitized solar cell. The charge-transfer resistance of the platinum/electrolyte interface as well as the capacitance of the electrical double layer (C{sub dl}) have been calculated from impedance measurements. Electrolytes with reduced content of polymer (2.5 wt.%) were doped with Al{sub 2}O{sub 3} particles of different sizes (50 nm, 300 nm, 1 {mu}m). The dispersion of the particles proceeds by speedy stirring of the hot electrolyte and the addition of PAN provides a homogeneous suspension. The addition of Al{sub 2}O{sub 3} particles causes a slight increase of the triiodide diffusion constants. Furthermore the suggested enhancement of the charge transfer rate shows a dependence on the size of the particles. (author)

  8. Light-Modulation of the Charge Injection in a Polymer Thin-Film Transistor by Functionalizing the Electrodes with Bistable Photochromic Self-Assembled Monolayers.

    Science.gov (United States)

    Mosciatti, Thomas; Del Rosso, Maria G; Herder, Martin; Frisch, Johannes; Koch, Norbert; Hecht, Stefan; Orgiu, Emanuele; Samorì, Paolo

    2016-08-01

    High fatigue resistance, bistability, and drastic property changes among isomers allow efficient modulation of the current output of organic thin-film transistors (OTFTs) to be obtained by a photogating of the charge-injection mechanism.

  9. Ultralocality on the lattice

    CERN Document Server

    Campos, R G; Campos, Rafael G.; Tututi, Eduardo S.

    2002-01-01

    It is shown that the nonlocal Dirac operator yielded by a lattice model that preserves chiral symmetry and uniqueness of fields, approaches to an ultralocal and invariant under translations operator when the size of the lattice tends to zero.

  10. New integrable lattice hierarchies

    Energy Technology Data Exchange (ETDEWEB)

    Pickering, Andrew [Area de Matematica Aplicada, ESCET, Universidad Rey Juan Carlos, c/ Tulipan s/n, 28933 Mostoles, Madrid (Spain); Zhu Zuonong [Departamento de Matematicas, Universidad de Salamanca, Plaza de la Merced 1, 37008 Salamanca (Spain) and Department of Mathematics, Shanghai Jiao Tong University, Shanghai 200030 (China)]. E-mail: znzhu2@yahoo.com.cn

    2006-01-23

    In this Letter we give a new integrable four-field lattice hierarchy, associated to a new discrete spectral problem. We obtain our hierarchy as the compatibility condition of this spectral problem and an associated equation, constructed herein, for the time-evolution of eigenfunctions. We consider reductions of our hierarchy, which also of course admit discrete zero curvature representations, in detail. We find that our hierarchy includes many well-known integrable hierarchies as special cases, including the Toda lattice hierarchy, the modified Toda lattice hierarchy, the relativistic Toda lattice hierarchy, and the Volterra lattice hierarchy. We also obtain here a new integrable two-field lattice hierarchy, to which we give the name of Suris lattice hierarchy, since the first equation of this hierarchy has previously been given by Suris. The Hamiltonian structure of the Suris lattice hierarchy is obtained by means of a trace identity formula.

  11. Reversible Charge Trapping in Bis-Carbazole-Diimide Redox Polymers with Complete Luminescence Quenching Enabling Nondestructive Read-Out by Resonance Raman Spectroscopy

    NARCIS (Netherlands)

    Kortekaas, Luuk; Lancia, Federico; Steen, Jorn D; Browne, Wesley R

    2017-01-01

    The coupling of substituted carbazole compounds through carbon-carbon bond formation upon one-electron oxidation is shown to be a highly versatile approach to the formation of redox polymer films. Although the polymerization of single carbazole units has been proposed earlier, we show that by

  12. Sober Topological Molecular Lattices

    Institute of Scientific and Technical Information of China (English)

    张德学; 李永明

    2003-01-01

    A topological molecular lattice (TML) is a pair (L, T), where L is a completely distributive lattice and r is a subframe of L. There is an obvious forgetful functor from the category TML of TML's to the category Loc of locales. In this note,it is showed that this forgetful functor has a right adjoint. Then, by this adjunction,a special kind of topological molecular lattices called sober topological molecular lattices is introduced and investigated.

  13. Infinite resistive lattices

    NARCIS (Netherlands)

    Atkinson, D; van Steenwijk, F.J.

    The resistance between two arbitrary nodes in an infinite square lattice of:identical resistors is calculated, The method is generalized to infinite triangular and hexagonal lattices in two dimensions, and also to infinite cubic and hypercubic lattices in three and more dimensions. (C) 1999 American

  14. Lattice Regularization and Symmetries

    CERN Document Server

    Hasenfratz, Peter; Von Allmen, R; Allmen, Reto von; Hasenfratz, Peter; Niedermayer, Ferenc

    2006-01-01

    Finding the relation between the symmetry transformations in the continuum and on the lattice might be a nontrivial task as illustrated by the history of chiral symmetry. Lattice actions induced by a renormalization group procedure inherit all symmetries of the continuum theory. We give a general procedure which gives the corresponding symmetry transformations on the lattice.

  15. Hadron structure from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Green, Jeremy [Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz (Germany)

    2016-01-22

    Recent progress in lattice QCD calculations of nucleon structure will be presented. Calculations of nucleon matrix elements and form factors have long been difficult to reconcile with experiment, but with advances in both methodology and computing resources, this situation is improving. Some calculations have produced agreement with experiment for key observables such as the axial charge and electromagnetic form factors, and the improved understanding of systematic errors will help to increase confidence in predictions of unmeasured quantities. The long-omitted disconnected contributions are now seeing considerable attention and some recent calculations of them will be discussed.

  16. Hadron Structure from Lattice QCD

    CERN Document Server

    Green, Jeremy

    2014-01-01

    Recent progress in lattice QCD calculations of nucleon structure will be presented. Calculations of nucleon matrix elements and form factors have long been difficult to reconcile with experiment, but with advances in both methodology and computing resources, this situation is improving. Some calculations have produced agreement with experiment for key observables such as the axial charge and electromagnetic form factors, and the improved understanding of systematic errors will help to increase confidence in predictions of unmeasured quantities. The long-omitted disconnected contributions are now seeing considerable attention and some recent calculations of them will be discussed.

  17. Direct observation of UV-induced charge accumulation in inverted-type polymer solar cells with a TiOx layer: Microscopic elucidation of the light-soaking phenomenon

    Science.gov (United States)

    Son, D.; Kuwabara, T.; Takahashi, K.; Marumoto, K.

    2016-09-01

    The mechanism of light-soaking phenomenon in inverted-type organic solar cells (IOSCs) with a structure of indium-tin-oxide/TiOx/P3HT:PCBM/Au was studied by electron spin resonance (ESR) spectroscopy. Charge accumulation in the cell during UV-light irradiation was observed using ESR, which was clearly correlated with the light-soaking phenomenon. The origin of the charge accumulation is clarified as holes that are deeply trapped at p-type P3HT polymer-chain ends with bromine after hole transfer from the band excitation in the TiOx layer. The holes are considered to be electrostatically attracted to trapped electrons in the TiOx layer after the band excitation. These accumulated charges are the origin of the light-soaking phenomenon. Our results strongly suggest that passivation of the residual OH groups in the TiOx layer is needed to avoid the light-soaking phenomenon by preventing electron trappings, a step that is indispensable in the operation of highly stable IOSCs without UV-light irradiation based on a low-cost and low-temperature device fabrication process using flexible plastic substrates.

  18. Lattice-Boltzmann-based Simulations of Diffusiophoresis

    Science.gov (United States)

    Castigliego, Joshua; Kreft Pearce, Jennifer

    We present results from a lattice-Boltzmann-base Brownian Dynamics simulation on diffusiophoresis and the separation of particles within the system. A gradient in viscosity that simulates a concentration gradient in a dissolved polymer allows us to separate various types of particles by their deformability. As seen in previous experiments, simulated particles that have a higher deformability react differently to the polymer matrix than those with a lower deformability. Therefore, the particles can be separated from each other. This simulation, in particular, was intended to model an oceanic system where the particles of interest were zooplankton, phytoplankton and microplastics. The separation of plankton from the microplastics was achieved.

  19. Physics of photorefraction in polymers

    CERN Document Server

    West, Dave

    2004-01-01

    Photorefractive polymer composites are an unusually sensitive class of photopolymers. Physics of Photorefraction in Polymers describes our current understanding of the physical processes that produce a photorefractive effect in key composite materials. Topics as diverse as charge generation, dispersive charge transport, charge compensation and trapping, molecular diffusion, organic composite structure, and nonlinear optical wave coupling are all developed from a physical perspective. Emphasis is placed on explaining how these physical processes lead to observable properties of the polymers, and the authors discuss various applications, including holographic archiving.

  20. Macrokinetic calculation of the ignition of a solid-fuel charge of glycidyl azide polymer in the mini-engine of a microelectromechanical system

    Science.gov (United States)

    Fut'ko, S. I.; Ermolaeva, E. M.; Dobrego, K. V.; Bondarenko, V. P.; Dolgii, L. N.

    2011-11-01

    The process of ignition of the solid fuel from glycidyl azide polymer in the mini-engine of a microelectromechanical system has been considered. Macrokinetic calculations of the self-ignition temperature of the fuel and the induction period for different heat transfer conditions have been made. On the basis of the critical thermal flux determination, recommendations on the choice of the minimum power and size of the thermistor in the igniter of the solid-fuel mini-engine have been formulated.

  1. Comparison of the operation of polymer/fullerene, polymer/polymer, and polymer/nanocrystal solar cells: a transient photocurrent and photovoltage study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhe; Gao, Feng; Greenham, Neil C.; McNeill, Christopher R. [Cavendish Laboratory, University of Cambridge, J J Thomson Ave, Cambridge, CB3 0HE (United Kingdom)

    2011-04-22

    We utilize transient techniques to directly compare the operation of polymer/fullerene, polymer/nanocrystal, and polymer/polymer bulk heterojunction solar cells. For all devices, poly(3-hexylthiophene) (P3HT) is used as the electron donating polymer, in combination with either the fullerene derivative phenyl-C{sub 61}-butyric acid methyl ester (PCBM) in polymer/fullerene cells, CdSe nanoparticles in polymer/nanocrystal cells, or the polyfluorene copolymer poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2,2-diyl) (F8TBT) in polymer/polymer cells. Transient photocurrent and photovoltage measurements are used to probe the dynamics of charge-separated carriers, with vastly different dynamic behavior observed for polymer/fullerene, polymer/polymer, and polymer/nanocrystal devices on the microsecond to millisecond timescale. Furthermore, by employing transient photocurrent analysis with different applied voltages we are also able to probe the dynamics behavior of these cells from short circuit to open circuit. P3HT/F8TBT and P3HT/CdSe devices are characterized by poor charge extraction of the long-lived carriers attributed to charge trapping. P3HT/PCBM devices, in contrast, show relatively trap-free operation with the variation in the photocurrent decay kinetics with applied bias at low intensity, consistent with the drift of free charges under a uniform electric field. Under solar conditions at the maximum power point, we see direct evidence of bimolecular recombination in the P3HT/PCBM device competing with charge extraction. Transient photovoltage measurements reveal that, at open circuit, photogenerated charges have similar lifetimes in all device types, and hence, the extraction of these long-lived charges is a limiting process in polymer/nanocrystal and polymer/polymer devices. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Charge transport in high-performance ink-jet printed single-droplet organic transistors based on a silylethynyl substituted pentacene/insulating polymer blend

    NARCIS (Netherlands)

    Li, X.; Smaal, W.T.T.; Kjellander, C.; Putten, B. van der; Gualandris, K.; Smits, E.C.P.; Anthony, J.; Broer, D.J.; Blom, P.W.M.; Genoe, J.; Gelinck, G.H.

    2011-01-01

    We present a systematic study of the influence of material composition and ink-jet processing conditions on the charge transport in bottom-gate field-effect transistors based on blends of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-PEN) and polystyrene. After careful process optimizations of

  3. Magnetization plateaus of dipolar spin ice on kagome lattice

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Y. L.; Wang, Y. L.; Yan, Z. B.; Liu, J.-M., E-mail: liujm@nju.edu.cn [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

    2014-05-07

    Unlike spin ice on pyrochlore lattice, the spin ice structure on kagome lattice retains net magnetic charge, indicating non-negligible dipolar interaction in modulating the spin ice states. While it is predicted that the dipolar spin ice on kagome lattice exhibits a ground state with magnetic charge order and √3 × √3 spin order, our work focuses on the magnetization plateau of this system. By employing the Wang-Landau algorithm, it is revealed that the lattice exhibits the fantastic three-step magnetization in response to magnetic field h along the [10] and [01] directions, respectively. For the h//[1 0] case, an additional √3/6M{sub s} step, where M{sub s} is the saturated magnetization, is observed in a specific temperature range, corresponding to a new state with charge order and short-range spin order.

  4. Polymer films

    Science.gov (United States)

    Granick, Steve; Sukhishvili, Svetlana A.

    2004-05-25

    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  5. Polymer films

    Science.gov (United States)

    Granick, Steve; Sukhishvili, Svetlana A.

    2008-12-30

    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  6. Axial Nucleon form factors from lattice QCD

    CERN Document Server

    Alexandrou, C; Carbonell, J; Constantinou, M; Harraud, P A; Guichon, P; Jansen, K; Korzec, T; Papinutto, M

    2010-01-01

    We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length $L=2.1$ fm and $L=2.8$ fm. Cut-off effects are investigated using three different values of the lattice spacings, namely $a=0.089$ fm, $a=0.070$ fm and $a=0.056$ fm. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment.

  7. Creation of Superheterojunction Polymers via Direct Polycondensation: Segregated and Bicontinuous Donor-Acceptor π-Columnar Arrays in Covalent Organic Frameworks for Long-Lived Charge Separation.

    Science.gov (United States)

    Jin, Shangbin; Supur, Mustafa; Addicoat, Matthew; Furukawa, Ko; Chen, Long; Nakamura, Toshikazu; Fukuzumi, Shunichi; Irle, Stephan; Jiang, Donglin

    2015-06-24

    By developing metallophthalocyanines and diimides as electron-donating and -accepting building blocks, herein, we report the construction of new electron donor-acceptor covalent organic frameworks (COFs) with periodically ordered electron donor and acceptor π-columnar arrays via direct polycondensation reactions. X-ray diffraction measurements in conjunction with structural simulations resolved that the resulting frameworks consist of metallophthalocyanine and diimide columns, which are ordered in a segregated yet bicontinuous manner to form built-in periodic π-arrays. In the frameworks, each metallophthalocyanine donor and diimide acceptor units are exactly linked and interfaced, leading to the generation of superheterojunctions-a new type of heterojunction machinery, for photoinduced electron transfer and charge separation. We show that this polycondensation method is widely applicable to various metallophthalocyanines and diimides as demonstrated by the combination of copper, nickel, and zinc phthalocyanine donors with pyrommellitic diimide, naphthalene diimide, and perylene diimide acceptors. By using time-resolved transient absorption spectroscopy and electron spin resonance, we demonstrated that the COFs enable long-lived charge separation, whereas the metal species, the class of acceptors, and the local geometry between donor and acceptor units play roles in determining the photochemical dynamics. The results provide insights into photoelectric COFs and demonstrate their enormous potential for charge separation and photoenergy conversions.

  8. Jammed lattice sphere packings

    OpenAIRE

    Kallus, Yoav; Marcotte, Étienne; Torquato, Salvatore

    2013-01-01

    We generate and study an ensemble of isostatic jammed hard-sphere lattices. These lattices are obtained by compression of a periodic system with an adaptive unit cell containing a single sphere until the point of mechanical stability. We present detailed numerical data about the densities, pair correlations, force distributions, and structure factors of such lattices. We show that this model retains many of the crucial structural features of the classical hard-sphere model and propose it as a...

  9. On Traveling Waves in Lattices: The Case of Riccati Lattices

    Science.gov (United States)

    Dimitrova, Zlatinka

    2012-09-01

    The method of simplest equation is applied for analysis of a class of lattices described by differential-difference equations that admit traveling-wave solutions constructed on the basis of the solution of the Riccati equation. We denote such lattices as Riccati lattices. We search for Riccati lattices within two classes of lattices: generalized Lotka-Volterra lattices and generalized Holling lattices. We show that from the class of generalized Lotka-Volterra lattices only the Wadati lattice belongs to the class of Riccati lattices. Opposite to this many lattices from the Holling class are Riccati lattices. We construct exact traveling wave solutions on the basis of the solution of Riccati equation for three members of the class of generalized Holling lattices.

  10. Twisted mass lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Shindler, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2007-07-15

    I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)

  11. 典型空间聚合物介质的抗内带电改性技术%Internal charging protection technology of typical space polymer dielectric material

    Institute of Scientific and Technical Information of China (English)

    王金锋; 郑晓泉; 李盛涛; 白婧婧

    2011-01-01

    消除航天器介质内带电所产生脉冲放电威胁的最佳方式,除有效屏蔽外,就是研制不会产生脉冲放电的介质材料和绝缘结构件.通过对航天器用聚酰亚胺、环氧树脂和聚四氟乙烯等几种典型聚合物的改性研究发现,采用微米级无机粉料对聚合物介质材料进行改性,只要添加剂的电导率显著低于聚合物的电导率,该复合介质材料即可产生显著的非线性电阻率特性,可以实现在介质内带电程度达到放电阈值时迅速以非脉冲电导电流方式释放掉所储存的危险电荷,有可能达到消除脉冲放电的目标;当该添加剂含有微量"施主"杂质时甚至还可以提高介质材料在正常情况下的电阻率.对复合介质非线性电阻特性的产生机理进行了分析.%Besides efficient shield, the best method for eliminating the pulsed discharge induced by the deep charge of spacecraft dielectric was to use dielectric materials or insulation structural components that never produce any pulsed discharges. By non-linearity modification experiment research on several typical polymer dielectrics like Polyimide, Epoxide resin and Teflon, it was found that through the addition of the inorganic powder that possess a conductivity much higher than that of the polymer, the composite dielectric material would produce a remarkable non-linearity conductance character. By this way,the excessive charges would be discharged as a method of non-pulsed conducting current before the deep dielectric charging reaches the discharge threshold. It was proved that, even the normal resistance could be increased by this method. Finally,the mechanism on the non-linearity conductance of the composite material was investigated.

  12. THE CORRELATION EFFECT ON THE CHAIN MOTION CONTRIBUTION TO IONIC TRANSPORT IN POLYMER ELECTROLYTES

    Institute of Scientific and Technical Information of China (English)

    XU Gu

    1994-01-01

    The ionic transport process in polymer electrolytes (such as polyethylene oxide) was simulated numerically on a two dimensional square lattice where charge carriers are accommodated by the lattice sites connected randomly with available bonds to represent the amorphous chain configuration. Following the dynamic bond percolation theory(DBPT),the chain motion contribution to the ionic conduction was incorporated via periodical renewal of the random bond configuration. To check and extend the prediction made by DBPT employing global abrupt bond renewal,spatial correlation of the bond reassignment was introduced to the system by:1)regional bond renewal and 2) organized bond motion. It is found that the difference between the diffusivities simulated involving regional bond renewal and those of DBPT becomes negligible when the bond renewal rate approaches the carrier hopping rate.

  13. 两种典型星用聚合物介质抗内带电改性防护技术研究%STUDY ON THE DEEP DIELECTRIC CHARGING PROTECTION TECHNOLOGY OF TWO TYPICAL POLYMERS ON SPACECRAFT

    Institute of Scientific and Technical Information of China (English)

    乌江; 康亚丽; 张振军; 郑晓泉

    2012-01-01

    空间高能电子辐射易造成星用聚合物介质内带电水平过高,是卫星运行可靠性的潜在威胁因素.对航天器介质材料进行非线性电导改性是提高航天器介质材料自释电荷能力,进而降低内带电水平的有效方法.实验选用半导电无机添加剂对典型空间聚合物材料聚四氟乙烯、聚酰亚胺进行改性工艺和电导特性研究,测量了常态体电导率与添加剂含量关系,不同含量添加剂下复合材料体电导率随温度与电场的变化规律以及复合材料的导热性能参数.实验表明,添加剂含量会显著影响复合材料的体电导特性及导热特性,特别是复合材料的非线性电导特性阈值电场降低最为明显.这种既能保持高绝缘性能又具有良好非线性电导特性的新型复合介质材料,有希望成为从根本上解决星用聚合物介质深层带电问题的有效措施.%The high-energy electron radiation can easily lead to the high level of deep dielectric charging in spacecraft used polymers, which is the potential threat to the operation of spacecraft. The conduction modification is an effective method to raise the charge releasing ability of the material and lower down the level of deep dielectric charging. A kind of semi-conductive inorganic filler is doped into the two typical spacecraft polymers, polytetrafluoroethylene ( PTFE) and polyimide ( PI) , and the processing technology and conduction properties of the composites were studied. The normal state conductivity, the temperature-dependent conduction property, the nonlinear conduction property and the thermal conductivity of the composites with different filler contents were measured. The experimental results indicate that, the electrical conduction and the thermal conduction are both influenced by the inorganic filler, especially the threshold field of the nonlinear conduction property drops obviously. The composites, possessing the high insulation and nonlinear

  14. Photorefractive polymers with low intrinsic trap density

    NARCIS (Netherlands)

    Bolink, HJ; Krasnikov, VV; Hadziioannou, G; Ducharme, S; Stasiak, JW

    1997-01-01

    Two novel photorefractive polymers are presented, based on the charge transport molecule N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD). In one polymer the TPD unit is chemically modified so that it can function both as charge transport and as electro-optic molecule. In

  15. Electrochemical analysis of the alterations in copper pigments using charge transfer coefficient/peak potential diagrams. Application to microsamples of baroque wall paintings attached to polymer film electrodes.

    Science.gov (United States)

    Doménech-Carbó, A; Doménech-Carbó, M T; Gimeno-Adelantado, J V; Bosch-Reig, F; Saurí-Peris, M C; Casas-Catalán, M J

    2001-04-01

    The alteration of copper pigments in art samples was studied by linear scan and cyclic voltammetry using sample-modified Elvacite 2044 film electrodes on the basis of two-dimensional diagrams of charge transfer coefficients calculated from Tafel plots of reductive dissolution processes vs. peak potential. Characteristic voltammetric peaks were obtained for pigments used in the baroque vault frescoes of the Basílica de la Virgen de los Desamparados painted by Antonio Palomino. Results obtained by voltammetric techniques were compared with those from SEM/EDX and FT-IR analysis obtaining a good agreement and leaving to an unambiguous identification of pigments used by Palomino and their alteration products.

  16. Strangeness at finite temperature from Lattice QCD

    CERN Document Server

    Noronha-Hostler, Jacquelyn; Gunther, Jana; Parotto, Paolo; Pasztor, Attila; Vazquez, Israel Portillo; Ratti, Claudia

    2016-01-01

    The precision reached by recent lattice QCD results allows for the first time to investigate whether the measured hadronic spectrum is missing some additional strange states, which are predicted by the Quark Model but have not yet been detected. This can be done by comparing some sensitive thermodynamic observables from lattice QCD to the predictions of the Hadron Resonance Gas model (with the inclusion of decays [3]). We propose a set of specific observables, defined as linear combinations of conserved charge fluctuations, which allow to investigate this issue for baryons containing one or more strange quarks separately. Applications of these observables to isolate the multiplicity fluctuations of kaons from lattice QCD, and their comparison with the experimental results, are also discussed.

  17. Nanoimprinted polymer photonic crystal dye lasers

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Smith, Cameron; Buss, Thomas

    2010-01-01

    Optically pumped polymer photonic crystal band-edge dye lasers are presented. The photonic crystal is a rectangular lattice providing laser feedback as well as an optical resonance for the pump light. The lasers are defined in a thin film of photodefinable Ormocore hybrid polymer, doped...... with the laser dye Pyrromethene 597. A compact frequency doubled Nd:YAG laser (352 nm, 5 ns pulses) is used to pump the lasers from above the chip. The laser devices are 450 nm thick slab waveguides with a rectangular lattice of 100 nm deep air holes imprinted into the surface. The 2-dimensional rectangular...... lattice is described by two orthogonal unit vectors of length a and b, defining the P and X directions. The frequency of the laser can be tuned via the lattice constant a (187 nm - 215 nm) while pump light is resonantly coupled into the laser from an angle () depending on the lattice constant b (355 nm...

  18. Nuclear lattice simulations

    Directory of Open Access Journals (Sweden)

    Epelbaum E.

    2010-04-01

    Full Text Available We review recent progress on nuclear lattice simulations using chiral effective field theory. We discuss lattice results for dilute neutron matter at next-to-leading order, three-body forces at next-to-next-toleading order, isospin-breaking and Coulomb effects, and the binding energy of light nuclei.

  19. Electrically conducting polymers for aerospace applications

    Science.gov (United States)

    Meador, Mary Ann B.; Gaier, James R.; Good, Brian S.; Sharp, G. R.; Meador, Michael A.

    1991-01-01

    Current research on electrically conducting polymers from 1974 to the present is reviewed focusing on the development of materials for aeronautic and space applications. Problems discussed include extended pi-systems, pyrolytic polymers, charge-transfer systems, conductive matrix resins for composite materials, and prospects for the use of conducting polymers in space photovoltaics.

  20. Conjugate polymers and electronic conductive polymers; Polymeres conjugues et polymeres conducteurs electroniques

    Energy Technology Data Exchange (ETDEWEB)

    Attias, A.J. [Universite Pierre et Marie Curie, Lab. de Chimie Macromoleculaire, UMR 7610 - CNRS, 75 - Paris (France)

    2002-05-01

    In some certain conditions a plastic material can become conductive (synthetic metal). To become conductive, a polymer must be conjugate (alternance of simple and multiple bonds) and doped (electron removal or addition). This article presents the recent advances and trends of the research on conductive polymers. The role of {pi} electrons in the conjugate systems is recalled in a first part. The description of energy states of conjugate polymers in terms of bands structure allow to consider them as organic semiconductors. Thus, it is possible to generate charged species by doping, charge injection or photo-excitation. These charge carriers, the conduction mechanisms and the related applications are presented. The chemistry and synthesis of these polymers are presented in a second part: 1 - evolution of research; 2 - physics of conductive polymers (role of {pi} electrons in conjugate polymers, {pi}-electrons conjugate compounds, influence of conjugation length and notion of bands structure, charges-doping generation, conductive polymers, chemical doping and electrical conduction, charge injection at the conjugate semiconductor metal-polymer interface: electro-luminescent polymers, charge creation by photo-excitation: polymers for photovoltaic cells); 3 - chemistry of conductive polymers (role of synthesis, monomers choice, other trends). (J.S.)

  1. Visualization Tools for Lattice QCD - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Massimo Di Pierro

    2012-03-15

    Our research project is about the development of visualization tools for Lattice QCD. We developed various tools by extending existing libraries, adding new algorithms, exposing new APIs, and creating web interfaces (including the new NERSC gauge connection web site). Our tools cover the full stack of operations from automating download of data, to generating VTK files (topological charge, plaquette, Polyakov lines, quark and meson propagators, currents), to turning the VTK files into images, movies, and web pages. Some of the tools have their own web interfaces. Some Lattice QCD visualization have been created in the past but, to our knowledge, our tools are the only ones of their kind since they are general purpose, customizable, and relatively easy to use. We believe they will be valuable to physicists working in the field. They can be used to better teach Lattice QCD concepts to new graduate students; they can be used to observe the changes in topological charge density and detect possible sources of bias in computations; they can be used to observe the convergence of the algorithms at a local level and determine possible problems; they can be used to probe heavy-light mesons with currents and determine their spatial distribution; they can be used to detect corrupted gauge configurations. There are some indirect results of this grant that will benefit a broader audience than Lattice QCD physicists.

  2. Extracting Electric Polarizabilities from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Will Detmold, William Detmold, Brian Tiburzi, Andre Walker-Loud

    2009-05-01

    Charged and neutral, pion and kaon electric polarizabilities are extracted from lattice QCD using an ensemble of anisotropic gauge configurations with dynamical clover fermions. We utilize classical background fields to access the polarizabilities from two-point correlation functions. Uniform background fields are achieved by quantizing the electric field strength with the proper treatment of boundary flux. These external fields, however, are implemented only in the valence quark sector. A novel method to extract charge particle polarizabilities is successfully demonstrated for the first time.

  3. Anisotropic Kondo lattice without Nozieres exhaustion effect

    Energy Technology Data Exchange (ETDEWEB)

    Kiselev, M.N. [Physics Department, Arnold Sommerfeld Center for Theoretical Physics and Center for Nano-Science, Ludwig-Maximilians Universitaet Muenchen, 80333 Munich (Germany)]. E-mail: kiselev@physik.uni-wuerzburg.de; Kikoin, K. [Ben-Gurion University of the Negev, Beer-Sheva, 84105 (Israel)]. E-mail: kikoin@bgumail.bgu.ac.il

    2006-05-01

    The properties of layered Anderson/Kondo lattices with metallic electrons confined in 2D xy planes and local spins in insulating layers forming chains in z direction are studied. Each spin possesses its own 2D Kondo cloud, so that the Nozieres' exhaustion problem does not arise. The excitation spectrum is gapless both in charge and spin sectors. Possible experimental realizations of the model are briefly discussed.

  4. Substrate Temperature Effect on Charge Transport Performance of ZnO Electron Transport Layer Prepared by a Facile Ultrasonic Spray Pyrolysis in Polymer Solar Cells

    Directory of Open Access Journals (Sweden)

    Jiang Cheng

    2015-01-01

    Full Text Available A novel ultrasonic spray pyrolysis for high-quality ZnO films based on zinc-ammonia solution was achieved in air. To investigate the structural and optical properties as well as the performance of polymer solar cells (PSCs, ZnO films at different substrate temperatures and thicknesses were prepared. The performance of poly(3-hexylthiophene:[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM based PSC was found to be improved due to the ZnO films. The crystal structure and roughness of the ZnO films fabricated at different temperatures were found to affect the performance of PSCs. The optimized power conversion efficiency was found to be maximum for PSCs with ZnO films prepared at 200°C. The growth process of these ZnO films is very simple, cost-effective, and compatible for larger-scale PSC preparation. The precursor used for spray pyrolysis is environmentally friendly and helps to achieve ZnO film preparation at a relative low temperature.

  5. Charge-separation enhancement in inverted polymer solar cells by molecular-level triple heterojunction: NiO-np:P3HT:PCBM.

    Science.gov (United States)

    Pradeep, U W; Villani, M; Calestani, D; Cristofolini, L; Iannotta, S; Zappettini, A; Coppedè, N

    2017-01-20

    Hole collection and transport are crucial physical processes in bulk-heterojunction (BHJ) solar cells, which represent major bottlenecks due to their limitations in power conversion efficiency (PCE). Hence, a more efficient alternative is needed to accept and transport holes to the collection electrode in BHJ solar cells. Here, we bring both electron and hole collection centres close to the point of exciton generation by infiltrating P3HT poly(3-hexylthiophene):PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) blend into a highly porous interconnected p-type NiO-nanoparticle (NiO-np) network, through solvent-assisted grafting. In this study, a hybrid polymer solar cell is demonstrated with a P3HT:PCBM:NiO-np triple-heterojunction active layer which showed greatly improved rectification behaviour, long electron lifetime and generated higher PCE of 4% under AM 1.5 solar illumination with a 75% increase in PCE with respect to the P3HT:PCBM device. The optimum NiO-np amount and active-layer thickness were found to be 2% and 250 nm, respectively.

  6. Charge-separation enhancement in inverted polymer solar cells by molecular-level triple heterojunction: NiO-np:P3HT:PCBM

    Science.gov (United States)

    Pradeep, U. W.; Villani, M.; Calestani, D.; Cristofolini, L.; Iannotta, S.; Zappettini, A.; Coppedè, N.

    2017-01-01

    Hole collection and transport are crucial physical processes in bulk-heterojunction (BHJ) solar cells, which represent major bottlenecks due to their limitations in power conversion efficiency (PCE). Hence, a more efficient alternative is needed to accept and transport holes to the collection electrode in BHJ solar cells. Here, we bring both electron and hole collection centres close to the point of exciton generation by infiltrating P3HT poly(3-hexylthiophene):PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) blend into a highly porous interconnected p-type NiO-nanoparticle (NiO-np) network, through solvent-assisted grafting. In this study, a hybrid polymer solar cell is demonstrated with a P3HT:PCBM:NiO-np triple-heterojunction active layer which showed greatly improved rectification behaviour, long electron lifetime and generated higher PCE of 4% under AM 1.5 solar illumination with a 75% increase in PCE with respect to the P3HT:PCBM device. The optimum NiO-np amount and active-layer thickness were found to be 2% and 250 nm, respectively.

  7. Techniques for transparent lattice measurement and correction

    Science.gov (United States)

    Cheng, Weixing; Li, Yongjun; Ha, Kiman

    2017-07-01

    A novel method has been successfully demonstrated at NSLS-II to characterize the lattice parameters with gated BPM turn-by-turn (TbT) capability. This method can be used at high current operation. Conventional lattice characterization and tuning are carried out at low current in dedicated machine studies which include beam-based measurement/correction of orbit, tune, dispersion, beta-beat, phase advance, coupling etc. At the NSLS-II storage ring, we observed lattice drifting during beam accumulation in user operation. Coupling and lifetime change while insertion device (ID) gaps are moved. With the new method, dynamical lattice correction is possible to achieve reliable and productive operations. A bunch-by-bunch feedback system excites a small fraction (∼1%) of bunches and gated BPMs are aligned to see those bunch motions. The gated TbT position data are used to characterize the lattice hence correction can be applied. As there are ∼1% of total charges disturbed for a short period of time (several ms), this method is transparent to general user operation. We demonstrated the effectiveness of these tools during high current user operation.

  8. Grafted polymer under shear flow

    Science.gov (United States)

    Kumar, Sanjiv; Foster, Damien P.; Giri, Debaprasad; Kumar, Sanjay

    2016-04-01

    A self-attracting-self-avoiding walk model of polymer chain on a square lattice has been used to gain an insight into the behaviour of a polymer chain under shear flow in a slit of width L. Using exact enumeration technique, we show that at high temperature, the polymer acquires the extended state continuously increasing with shear stress. However, at low temperature the polymer exhibits two transitions: a transition from the coiled to the globule state and a transition to a stem-flower like state. For a chain of finite length, we obtained the exact monomer density distributions across the layers at different temperatures. The change in density profile with shear stress suggests that the polymer under shear flow can be used as a molecular gate with potential application as a sensor.

  9. Modified Lattice Landau Gauge

    CERN Document Server

    Von Smekal, L; Sternbeck, A; Williams, A G

    2007-01-01

    We propose a modified lattice Landau gauge based on stereographically projecting the link variables on the circle S^1 -> R for compact U(1) or the 3-sphere S^3 -> R^3 for SU(2) before imposing the Landau gauge condition. This can reduce the number of Gribov copies exponentially and solves the Gribov problem in compact U(1) where it is a lattice artifact. Applied to the maximal Abelian subgroup this might be just enough to avoid the perfect cancellation amongst the Gribov copies in a lattice BRST formulation for SU(N), and thus to avoid the Neuberger 0/0 problem. The continuum limit of the Landau gauge remains unchanged.

  10. Jammed lattice sphere packings.

    Science.gov (United States)

    Kallus, Yoav; Marcotte, Étienne; Torquato, Salvatore

    2013-12-01

    We generate and study an ensemble of isostatic jammed hard-sphere lattices. These lattices are obtained by compression of a periodic system with an adaptive unit cell containing a single sphere until the point of mechanical stability. We present detailed numerical data about the densities, pair correlations, force distributions, and structure factors of such lattices. We show that this model retains many of the crucial structural features of the classical hard-sphere model and propose it as a model for the jamming and glass transitions that enables exploration of much higher dimensions than are usually accessible.

  11. Jammed lattice sphere packings

    Science.gov (United States)

    Kallus, Yoav; Marcotte, Étienne; Torquato, Salvatore

    2013-12-01

    We generate and study an ensemble of isostatic jammed hard-sphere lattices. These lattices are obtained by compression of a periodic system with an adaptive unit cell containing a single sphere until the point of mechanical stability. We present detailed numerical data about the densities, pair correlations, force distributions, and structure factors of such lattices. We show that this model retains many of the crucial structural features of the classical hard-sphere model and propose it as a model for the jamming and glass transitions that enables exploration of much higher dimensions than are usually accessible.

  12. Lasing at the band edges of plasmonic lattices

    NARCIS (Netherlands)

    Schokker, A.H.; Koenderink, A.F.

    2014-01-01

    We report room-temperature lasing in two-dimensional diffractive lattices of silver and gold plasmon particle arrays embedded in a dye-doped polymer that acts both as waveguide and gain medium. As compared to conventional dielectric distributed feedback (DFB) lasers, a central question is how the un

  13. Polymer fractionation

    Energy Technology Data Exchange (ETDEWEB)

    Hadermann, A. F.

    1985-04-09

    Soluble polymers are fractionated according to molecular weight by cryogenically comminuting the polymer and introducing the polymer particles, while still in the active state induced by cryogenic grinding, into a liquid having a solvent power selected to produce a coacervate fraction containing high molecular weight polymer species and a dilute polymer solution containing lower molecular weight polymer species. The coacervate may be physically separated from the solution and finds use in the production of antimisting jet fuels and the like.

  14. Biodegradable Polymers

    OpenAIRE

    Isabelle Vroman; Lan Tighzert

    2013-01-01

    Biodegradable materials are used in packaging, agriculture, medicine and other areas. In recent years there has been an increase in interest in biodegradable polymers. Two classes of biodegradable polymers can be distinguished: synthetic or natural polymers. There are polymers produced from feedstocks derived either from petroleum resources (non renewable resources) or from biological resources (renewable resources). In general natural polymers offer fewer advantages than synthetic polymers. ...

  15. Emergent lattices with geometrical frustration in doped extended Hubbard models

    Science.gov (United States)

    Kaneko, Ryui; Tocchio, Luca F.; Valentí, Roser; Gros, Claudius

    2016-11-01

    Spontaneous charge ordering occurring in correlated systems may be considered as a possible route to generate effective lattice structures with unconventional couplings. For this purpose we investigate the phase diagram of doped extended Hubbard models on two lattices: (i) the honeycomb lattice with on-site U and nearest-neighbor V Coulomb interactions at 3 /4 filling (n =3 /2 ) and (ii) the triangular lattice with on-site U , nearest-neighbor V , and next-nearest-neighbor V' Coulomb interactions at 3 /8 filling (n =3 /4 ). We consider various approaches including mean-field approximations, perturbation theory, and variational Monte Carlo. For the honeycomb case (i), charge order induces an effective triangular lattice at large values of U /t and V /t , where t is the nearest-neighbor hopping integral. The nearest-neighbor spin exchange interactions on this effective triangular lattice are antiferromagnetic in most of the phase diagram, while they become ferromagnetic when U is much larger than V . At U /t ˜(V/t ) 3 , ferromagnetic and antiferromagnetic exchange interactions nearly cancel out, leading to a system with four-spin ring-exchange interactions. On the other hand, for the triangular case (ii) at large U and finite V', we find no charge order for small V , an effective kagome lattice for intermediate V , and one-dimensional charge order for large V . These results indicate that Coulomb interactions induce [case (i)] or enhance [case(ii)] emergent geometrical frustration of the spin degrees of freedom in the system, by forming charge order.

  16. Electroactive polymers for sensing

    Science.gov (United States)

    2016-01-01

    Electromechanical coupling in electroactive polymers (EAPs) has been widely applied for actuation and is also being increasingly investigated for sensing chemical and mechanical stimuli. EAPs are a unique class of materials, with low-moduli high-strain capabilities and the ability to conform to surfaces of different shapes. These features make them attractive for applications such as wearable sensors and interfacing with soft tissues. Here, we review the major types of EAPs and their sensing mechanisms. These are divided into two classes depending on the main type of charge carrier: ionic EAPs (such as conducting polymers and ionic polymer–metal composites) and electronic EAPs (such as dielectric elastomers, liquid-crystal polymers and piezoelectric polymers). This review is intended to serve as an introduction to the mechanisms of these materials and as a first step in material selection for both researchers and designers of flexible/bendable devices, biocompatible sensors or even robotic tactile sensing units. PMID:27499846

  17. Lattice Gerbe Theory

    CERN Document Server

    Lipstein, Arthur E

    2014-01-01

    We formulate the theory of a 2-form gauge field on a Euclidean spacetime lattice. In this approach, the fundamental degrees of freedom live on the faces of the lattice, and the action can be constructed from the sum over Wilson surfaces associated with each fundamental cube of the lattice. If we take the gauge group to be $U(1)$, the theory reduces to the well-known abelian gerbe theory in the continuum limit. We also propose a very simple and natural non-abelian generalization with gauge group $U(N) \\times U(N)$, which gives rise to $U(N)$ Yang-Mills theory upon dimensional reduction. Formulating the theory on a lattice has several other advantages. In particular, it is possible to compute many observables, such as the expectation value of Wilson surfaces, analytically at strong coupling and numerically for any value of the coupling.

  18. Root lattices and quasicrystals

    Science.gov (United States)

    Baake, M.; Joseph, D.; Kramer, P.; Schlottmann, M.

    1990-10-01

    It is shown that root lattices and their reciprocals might serve as the right pool for the construction of quasicrystalline structure models. All noncrystallographic symmetries observed so far are covered in minimal embedding with maximal symmetry.

  19. SPIN ON THE LATTICE.

    Energy Technology Data Exchange (ETDEWEB)

    ORGINOS,K.

    2003-01-07

    I review the current status of hadronic structure computations on the lattice. I describe the basic lattice techniques and difficulties and present some of the latest lattice results; in particular recent results of the RBC group using domain wall fermions are also discussed. In conclusion, lattice computations can play an important role in understanding the hadronic structure and the fundamental properties of Quantum Chromodynamics (QCD). Although some difficulties still exist, several significant steps have been made. Advances in computer technology are expected to play a significant role in pushing these computations closer to the chiral limit and in including dynamical fermions. RBC has already begun preliminary dynamical domain wall fermion computations [49] which we expect to be pushed forward with the arrival of QCD0C. In the near future, we also expect to complete the non-perturbative renormalization of the relevant derivative operators in quenched QCD.

  20. Superalloy Lattice Block Structures

    Science.gov (United States)

    Nathal, M. V.; Whittenberger, J. D.; Hebsur, M. G.; Kantzos, P. T.; Krause, D. L.

    2004-01-01

    Initial investigations of investment cast superalloy lattice block suggest that this technology will yield a low cost approach to utilize the high temperature strength and environmental resistance of superalloys in lightweight, damage tolerant structural configurations. Work to date has demonstrated that relatively large superalloy lattice block panels can be successfully investment cast from both IN-718 and Mar-M247. These castings exhibited mechanical properties consistent with the strength of the same superalloys measured from more conventional castings. The lattice block structure also accommodates significant deformation without failure, and is defect tolerant in fatigue. The potential of lattice block structures opens new opportunities for the use of superalloys in future generations of aircraft applications that demand strength and environmental resistance at elevated temperatures along with low weight.

  1. Mechanical cloak design by direct lattice transformation.

    Science.gov (United States)

    Bückmann, Tiemo; Kadic, Muamer; Schittny, Robert; Wegener, Martin

    2015-04-21

    Spatial coordinate transformations have helped simplifying mathematical issues and solving complex boundary-value problems in physics for decades already. More recently, material-parameter transformations have also become an intuitive and powerful engineering tool for designing inhomogeneous and anisotropic material distributions that perform wanted functions, e.g., invisibility cloaking. A necessary mathematical prerequisite for this approach to work is that the underlying equations are form invariant with respect to general coordinate transformations. Unfortunately, this condition is not fulfilled in elastic-solid mechanics for materials that can be described by ordinary elasticity tensors. Here, we introduce a different and simpler approach. We directly transform the lattice points of a 2D discrete lattice composed of a single constituent material, while keeping the properties of the elements connecting the lattice points the same. After showing that the approach works in various areas, we focus on elastic-solid mechanics. As a demanding example, we cloak a void in an effective elastic material with respect to static uniaxial compression. Corresponding numerical calculations and experiments on polymer structures made by 3D printing are presented. The cloaking quality is quantified by comparing the average relative SD of the strain vectors outside of the cloaked void with respect to the homogeneous reference lattice. Theory and experiment agree and exhibit very good cloaking performance.

  2. A study of microtubule dipole lattices

    Science.gov (United States)

    Nandi, Shubhendu

    Microtubules are cytoskeletal protein polymers orchestrating a host of important cellular functions including, but not limited to, cell support, cell division, cell motility and cell transport. In this thesis, we construct a toy-model of the microtubule lattice composed of vector Ising spins representing tubulin molecules, the building block of microtubules. Nearest-neighbor and next-to-nearest neighbor interactions are considered within an anisotropic dielectric medium. As a consequence of the helical topology, we observe that certain spin orientations render the lattice frustrated with nearest neighbor ferroelectric and next-to-nearest neighbor antiferroelectric bonds. Under these conditions, the lattice displays the remarkable property of stabilizing certain spin patterns that are robust to thermal fluctuations. We model this behavior in the framework of a generalized Ising model known as the J1 - J2 model and theoretically determine the set of stable patterns. Employing Monte-Carlo methods, we demonstrate the stability of such patterns in the microtubule lattice at human physiological temperatures. This suggests a novel biological mechanism for storing information in living organisms, whereby the tubulin spin (dipole moment) states become information bits and information gets stored in microtubules in a way that is robust to thermal fluctuations.

  3. Lattice QCD for Baryon Rich Matter - Beyond Taylor Expansions

    Science.gov (United States)

    Bornyakov, V.; Boyda, D.; Goy, V.; Molochkov, A.; Nakamura, A.; Nikolaev, A.; Zakharov, V. I.

    2016-12-01

    We discuss our study for exploring the QCD phase diagram based on the lattice QCD. To go beyond the Taylor expansion and to reach higher density regions, we employ the canonical approach. In order to produce lattice data which meet experimental situation as much as possible, we propose a canonical approach with the charge and baryon number. We present our lattice QCD GPU code for this project which employs the clover improved Wilson fermions and Iwasaki gauge action to investigate pure imaginary chemical potential.

  4. Lattice QCD for Baryon Rich Matter – Beyond Taylor Expansions

    Energy Technology Data Exchange (ETDEWEB)

    Bornyakov, V. [ITEP, B. Cheremushkinskaya 25, Moscow, 117218 (Russian Federation); School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Boyda, D. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Goy, V. [School of Natural Sciences, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Molochkov, A. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Nakamura, A. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki, Osaka, 567-0047 (Japan); Theoretical Research Division, Nishina Center, RIKEN, Wako 351-0198 (Japan); Nikolaev, A. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Zakharov, V.I. [ITEP, B. Cheremushkinskaya 25, Moscow, 117218 (Russian Federation); School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Moscow Inst Phys & Technol, Dolgoprudny, Moscow Region, 141700 (Russian Federation)

    2016-12-15

    We discuss our study for exploring the QCD phase diagram based on the lattice QCD. To go beyond the Taylor expansion and to reach higher density regions, we employ the canonical approach. In order to produce lattice data which meet experimental situation as much as possible, we propose a canonical approach with the charge and baryon number. We present our lattice QCD GPU code for this project which employs the clover improved Wilson fermions and Iwasaki gauge action to investigate pure imaginary chemical potential.

  5. Vector Lattice Vortex Solitons

    Institute of Scientific and Technical Information of China (English)

    WANG Jian-Dong; YE Fang-Wei; DONG Liang-Wei; LI Yong-Ping

    2005-01-01

    @@ Two-dimensional vector vortex solitons in harmonic optical lattices are investigated. The stability properties of such solitons are closely connected to the lattice depth Vo. For small Vo, vector vortex solitons with the total zero-angular momentum are more stable than those with the total nonzero-angular momentum, while for large Vo, this case is inversed. If Vo is large enough, both the types of such solitons are stable.

  6. Technicolor on the Lattice

    CERN Document Server

    Pica, C; Lucini, B; Patella, A; Rago, A

    2009-01-01

    Technicolor theories provide an elegant mechanism for dynamical electroweak symmetry breaking. We will discuss the use of lattice simulations to study the strongly-interacting dynamics of some of the candidate theories, with matter fields in representations other than the fundamental. To be viable candidates for phenomenology, such theories need to be different from a scaled-up version of QCD, which were ruled out by LEP precision measurements, and represent a challenge for modern lattice computations.

  7. Automated Lattice Perturbation Theory

    Energy Technology Data Exchange (ETDEWEB)

    Monahan, Christopher

    2014-11-01

    I review recent developments in automated lattice perturbation theory. Starting with an overview of lattice perturbation theory, I focus on the three automation packages currently "on the market": HiPPy/HPsrc, Pastor and PhySyCAl. I highlight some recent applications of these methods, particularly in B physics. In the final section I briefly discuss the related, but distinct, approach of numerical stochastic perturbation theory.

  8. Permutohedral Lattice CNNs

    OpenAIRE

    Kiefel, Martin; Jampani, Varun; Gehler, Peter V.

    2014-01-01

    This paper presents a convolutional layer that is able to process sparse input features. As an example, for image recognition problems this allows an efficient filtering of signals that do not lie on a dense grid (like pixel position), but of more general features (such as color values). The presented algorithm makes use of the permutohedral lattice data structure. The permutohedral lattice was introduced to efficiently implement a bilateral filter, a commonly used image processing operation....

  9. Ultrafast Charge Photogeneration in MEH-PPV Charge-Transfer Complexes

    Science.gov (United States)

    Bakulin, Artem A.; Paraschuk, Dmitry Yu.; Pshenichnikov, Maxim S.; van Loosdrecht, Paul H. M.

    Visible-pump-IR-probe spectroscopy is used to study the ultrafast charge dynamics in MEH-PPV based charge-transfer complexes and donor-acceptor blends. Transient anisotropy of the polymer polaron band provides invaluable insights into excitation localisation and charge-transfer pathways.

  10. Charged Frenkel biexcitons in organic molecular crystals

    CERN Document Server

    Agranovich, V M; Kamchatnov, A M

    2001-01-01

    It is known that the energy of the lowest electronic transition in neutral molecules of anthracene, tetracene and other polyacenes is blue shifted in comparison with the corresponding transition energy in mono-valent molecular ions. This effect in molecular crystal may be responsible for the attraction between molecular (Frenkel) exciton and charge carrier. Due to this attraction the bound state of Frenkel exciton and free charge (charged Frenkel exciton) may be formed. The same mechanism can be responsible for formation of charged biexcitons (bound state of two Frenkel excitons and a charge carrier). Calculations are performed for molecular crystals like tetracene by means of one-dimensional lattice model

  11. Solitons in spiraling Vogel lattices

    CERN Document Server

    Kartashov, Yaroslav V; Torner, Lluis

    2012-01-01

    We address light propagation in Vogel optical lattices and show that such lattices support a variety of stable soliton solutions in both self-focusing and self-defocusing media, whose propagation constants belong to domains resembling gaps in the spectrum of a truly periodic lattice. The azimuthally-rich structure of Vogel lattices allows generation of spiraling soliton motion.

  12. Characterizing the Polymer:Fullerene Intermolecular Interactions

    KAUST Repository

    Sweetnam, Sean

    2016-02-02

    Polymer:fullerene solar cells depend heavily on the electronic coupling of the polymer and fullerene molecular species from which they are composed. The intermolecular interaction between the polymer and fullerene tends to be strong in efficient photovoltaic systems, as evidenced by efficient charge transfer processes and by large changes in the energetics of the polymer and fullerene when they are molecularly mixed. Despite the clear presence of these strong intermolecular interactions between the polymer and fullerene, there is not a consensus on the nature of these interactions. In this work, we use a combination of Raman spectroscopy, charge transfer state absorption, and density functional theory calculations to show that the intermolecular interactions do not appear to be caused by ground state charge transfer between the polymer and fullerene. We conclude that these intermolecular interactions are primarily van der Waals in nature. © 2016 American Chemical Society.

  13. Face-Centered-Cubic Nanostructured Polymer Foams

    Science.gov (United States)

    Cui, C.; Baughman, R. H.; Liu, L. M.; Zakhidov, A. A.; Khayrullin, I. I.

    1998-03-01

    Beautifully iridescent polymer foams having Fm-3m cubic symmetry and periodicities on the scale of the wavelength of light have been synthesized by the templating of porous synthetic opals. These fabrication processes involve the filling of porous SiO2 opals (with typical cubic lattice parameters of 250 nm) with either polymers or polymer precursors, polymerization of the precursors if necessary, and removal of the fcc array of SiO2 balls to provide an all-polymer structure. The structures of these foams are similar to periodic minimal surfaces, although the Gaussian curvature can have both positive and negative values. Depending upon whether the internal surfaces of the opal are polymer filled or polymer coated, the polymer replica has either one or two sets of independent channels. We fill these channels with semiconductors, metals, or superconductors to provide electronic and optical materials with novel properties dependent on the nanoscale periodicity.

  14. Biodegradable Polymers

    Directory of Open Access Journals (Sweden)

    Isabelle Vroman

    2009-04-01

    Full Text Available Biodegradable materials are used in packaging, agriculture, medicine and other areas. In recent years there has been an increase in interest in biodegradable polymers. Two classes of biodegradable polymers can be distinguished: synthetic or natural polymers. There are polymers produced from feedstocks derived either from petroleum resources (non renewable resources or from biological resources (renewable resources. In general natural polymers offer fewer advantages than synthetic polymers. The following review presents an overview of the different biodegradable polymers that are currently being used and their properties, as well as new developments in their synthesis and applications.

  15. Polymer electronics

    CERN Document Server

    Hsin-Fei, Meng

    2013-01-01

    Polymer semiconductor is the only semiconductor that can be processed in solution. Electronics made by these flexible materials have many advantages such as large-area solution process, low cost, and high performance. Researchers and companies are increasingly dedicating time and money in polymer electronics. This book focuses on the fundamental materials and device physics of polymer electronics. It describes polymer light-emitting diodes, polymer field-effect transistors, organic vertical transistors, polymer solar cells, and many applications based on polymer electronics. The book also disc

  16. A Bijection between Lattice-Valued Filters and Lattice-Valued Congruences in Residuated Lattices

    Directory of Open Access Journals (Sweden)

    Wei Wei

    2013-01-01

    Full Text Available The aim of this paper is to study relations between lattice-valued filters and lattice-valued congruences in residuated lattices. We introduce a new definition of congruences which just depends on the meet ∧ and the residuum →. Then it is shown that each of these congruences is automatically a universal-algebra-congruence. Also, lattice-valued filters and lattice-valued congruences are studied, and it is shown that there is a one-to-one correspondence between the set of all (lattice-valued filters and the set of all (lattice-valued congruences.

  17. Measuring on Lattices

    Science.gov (United States)

    Knuth, Kevin H.

    2009-12-01

    Previous derivations of the sum and product rules of probability theory relied on the algebraic properties of Boolean logic. Here they are derived within a more general framework based on lattice theory. The result is a new foundation of probability theory that encompasses and generalizes both the Cox and Kolmogorov formulations. In this picture probability is a bi-valuation defined on a lattice of statements that quantifies the degree to which one statement implies another. The sum rule is a constraint equation that ensures that valuations are assigned so as to not violate associativity of the lattice join and meet. The product rule is much more interesting in that there are actually two product rules: one is a constraint equation arises from associativity of the direct products of lattices, and the other a constraint equation derived from associativity of changes of context. The generality of this formalism enables one to derive the traditionally assumed condition of additivity in measure theory, as well introduce a general notion of product. To illustrate the generic utility of this novel lattice-theoretic foundation of measure, the sum and product rules are applied to number theory. Further application of these concepts to understand the foundation of quantum mechanics is described in a joint paper in this proceedings.

  18. Lattice theory of nonequilibrium fermion production

    Energy Technology Data Exchange (ETDEWEB)

    Gelfand, Daniil

    2014-07-22

    In this thesis we investigate non-equilibrium production of fermionic particles using modern lattice techniques. The presented applications range from preheating after inflation in the early Universe cosmology to pre-thermalization dynamics in heavy-ion collisions as well as pair production and string breaking in a lower-dimensional model of quantum chromodynamics. Strong enhancement of fermion production in the presence of overoccupied bosons is observed in scalar models undergoing instabilities. Both parametric resonance and tachyonic instability are considered as scenarios for preheating after inflation. The qualitative and quantitative features of the resulting fermion distribution are found to depend largely on an effective coupling parameter. In order to simulate fermions in three spatial dimensions we apply a stochastic low-cost lattice algorithm, which we verify by comparison with an exact lattice approach and with a functional method based on a coupling expansion. In the massive Schwinger model, we analyse the creation of fermion/anti-fermion pairs from homogeneous and inhomogeneous electric fields and observe string formation between charges. As a follow-up we study the dynamics of string breaking and establish a two-stage process, consisting of the initial particle production followed by subsequent charge separation and screening. In quantum chromodynamics, our focus lies on the properties of the quark sector during turbulent bosonic energy cascade as well as on the isotropization of quarks and gluons starting from different initial conditions.

  19. Adsorption and flocculation by polymers and polymer mixtures.

    Science.gov (United States)

    Gregory, John; Barany, Sandor

    2011-11-14

    Polymers of various types are in widespread use as flocculants in several industries. In most cases, polymer adsorption is an essential prerequisite for flocculation and kinetic aspects are very important. The rates of polymer adsorption and of re-conformation (relaxation) of adsorbed chains are key factors that influence the performance of flocculants and their mode of action. Polyelectrolytes often tend to adopt a rather flat adsorbed configuration and in this state their action is mainly through charge effects, including 'electrostatic patch' attraction. When the relaxation rate is quite low, particle collisions may occur while the adsorbed chains are still in an extended state and flocculation by polymer bridging may occur. These effects are now well understood and supported by much experimental evidence. In recent years there has been considerable interest in the use of multi-component flocculants, especially dual-polymer systems. In the latter case, there can be significant advantages over the use of single polymers. Despite some complications, there is a broad understanding of the action of dual polymer systems. In many cases the sequence of addition of the polymers is important and the pre-adsorbed polymer can have two important effects: providing adsorption sites for the second polymer or causing a more extended adsorbed conformation as a result of 'site blocking'. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. Lattice Boltzmann Stokesian dynamics.

    Science.gov (United States)

    Ding, E J

    2015-11-01

    Lattice Boltzmann Stokesian dynamics (LBSD) is presented for simulation of particle suspension in Stokes flows. This method is developed from Stokesian dynamics (SD) with resistance and mobility matrices calculated using the time-independent lattice Boltzmann algorithm (TILBA). TILBA is distinguished from the traditional lattice Boltzmann method (LBM) in that a background matrix is generated prior to the calculation. The background matrix, once generated, can be reused for calculations for different scenarios, thus the computational cost for each such subsequent calculation is significantly reduced. The LBSD inherits the merits of the SD where both near- and far-field interactions are considered. It also inherits the merits of the LBM that the computational cost is almost independent of the particle shape.

  1. Lattice gauge theories

    Science.gov (United States)

    Weisz, Peter; Majumdar, Pushan

    2012-03-01

    Lattice gauge theory is a formulation of quantum field theory with gauge symmetries on a space-time lattice. This formulation is particularly suitable for describing hadronic phenomena. In this article we review the present status of lattice QCD. We outline some of the computational methods, discuss some phenomenological applications and a variety of non-perturbative topics. The list of references is severely incomplete, the ones we have included are text books or reviews and a few subjectively selected papers. Kronfeld and Quigg (2010) supply a reasonably comprehensive set of QCD references. We apologize for the fact that have not covered many important topics such as QCD at finite density and heavy quark effective theory adequately, and mention some of them only in the last section "In Brief". These topics should be considered in further Scholarpedia articles.

  2. Improved Lattice Radial Quantization

    CERN Document Server

    Brower, Richard C; Fleming, George T

    2014-01-01

    Lattice radial quantization was proposed in a recent paper by Brower, Fleming and Neuberger[1] as a nonperturbative method especially suited to numerically solve Euclidean conformal field theories. The lessons learned from the lattice radial quantization of the 3D Ising model on a longitudinal cylinder with 2D Icosahedral cross-section suggested the need for an improved discretization. We consider here the use of the Finite Element Methods(FEM) to descretize the universally-equivalent $\\phi^4$ Lagrangian on $\\mathbb R \\times \\mathbb S^2$. It is argued that this lattice regularization will approach the exact conformal theory at the Wilson-Fisher fixed point in the continuum. Numerical tests are underway to support this conjecture.

  3. Graphene antidot lattice waveguides

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Gunst, Tue; Markussen, Troels

    2012-01-01

    We introduce graphene antidot lattice waveguides: nanostructured graphene where a region of pristine graphene is sandwiched between regions of graphene antidot lattices. The band gaps in the surrounding antidot lattices enable localized states to emerge in the central waveguide region. We model...... the waveguides via a position-dependent mass term in the Dirac approximation of graphene and arrive at analytical results for the dispersion relation and spinor eigenstates of the localized waveguide modes. To include atomistic details we also use a tight-binding model, which is in excellent agreement...... with the analytical results. The waveguides resemble graphene nanoribbons, but without the particular properties of ribbons that emerge due to the details of the edge. We show that electrons can be guided through kinks without additional resistance and that transport through the waveguides is robust against...

  4. Digital lattice gauge theories

    CERN Document Server

    Zohar, Erez; Reznik, Benni; Cirac, J Ignacio

    2016-01-01

    We propose a general scheme for a digital construction of lattice gauge theories with dynamical fermions. In this method, the four-body interactions arising in models with $2+1$ dimensions and higher, are obtained stroboscopically, through a sequence of two-body interactions with ancillary degrees of freedom. This yields stronger interactions than the ones obtained through pertubative methods, as typically done in previous proposals, and removes an important bottleneck in the road towards experimental realizations. The scheme applies to generic gauge theories with Lie or finite symmetry groups, both Abelian and non-Abelian. As a concrete example, we present the construction of a digital quantum simulator for a $\\mathbb{Z}_{3}$ lattice gauge theory with dynamical fermionic matter in $2+1$ dimensions, using ultracold atoms in optical lattices, involving three atomic species, representing the matter, gauge and auxiliary degrees of freedom, that are separated in three different layers. By moving the ancilla atoms...

  5. Optical Lattice Clocks

    Science.gov (United States)

    Oates, Chris

    2012-06-01

    Since they were first proposed in 2003 [1], optical lattice clocks have become one of the leading technologies for the next generation of atomic clocks, which will be used for advanced timing applications and in tests of fundamental physics [2]. These clocks are based on stabilized lasers whose frequency is ultimately referenced to an ultra-narrow neutral atom transition (natural linewidths magic'' value so as to yield a vanishing net AC Stark shift for the clock transition. As a result lattice clocks have demonstrated the capability of generating high stability clock signals with small absolute uncertainties (˜ 1 part in 10^16). In this presentation I will first give an overview of the field, which now includes three different atomic species. I will then use experiments with Yb performed in our laboratory to illustrate the key features of a lattice clock. Our research has included the development of state-of-the-art optical cavities enabling ultra-high-resolution optical spectroscopy (1 Hz linewidth). Together with the large atom number in the optical lattice, we are able to achieve very low clock instability (< 0.3 Hz in 1 s) [3]. Furthermore, I will show results from some of our recent investigations of key shifts for the Yb lattice clock, including high precision measurements of ultracold atom-atom interactions in the lattice and the dc Stark effect for the Yb clock transition (necessary for the evaluation of blackbody radiation shifts). [4pt] [1] H. Katori, M. Takamoto, V. G. Pal'chikov, and V. D. Ovsiannikov, Phys. Rev. Lett. 91, 173005 (2003). [0pt] [2] Andrei Derevianko and Hidetoshi Katori, Rev. Mod. Phys. 83, 331 (2011). [0pt] [3] Y. Y. Jiang, A. D. Ludlow, N. D. Lemke, R. W. Fox, J. A. Sherman, L.-S. Ma, and C. W. Oates, Nature Photonics 5, 158 (2011).

  6. Exact Lattice Supersymmetry

    Energy Technology Data Exchange (ETDEWEB)

    Catterall, Simon; Kaplan, David B.; Unsal, Mithat

    2009-03-31

    We provide an introduction to recent lattice formulations of supersymmetric theories which are invariant under one or more real supersymmetries at nonzero lattice spacing. These include the especially interesting case of N = 4 SYM in four dimensions. We discuss approaches based both on twisted supersymmetry and orbifold-deconstruction techniques and show their equivalence in the case of gauge theories. The presence of an exact supersymmetry reduces and in some cases eliminates the need for fine tuning to achieve a continuum limit invariant under the full supersymmetry of the target theory. We discuss open problems.

  7. Belief functions on lattices

    CERN Document Server

    Grabisch, Michel

    2008-01-01

    We extend the notion of belief function to the case where the underlying structure is no more the Boolean lattice of subsets of some universal set, but any lattice, which we will endow with a minimal set of properties according to our needs. We show that all classical constructions and definitions (e.g., mass allocation, commonality function, plausibility functions, necessity measures with nested focal elements, possibility distributions, Dempster rule of combination, decomposition w.r.t. simple support functions, etc.) remain valid in this general setting. Moreover, our proof of decomposition of belief functions into simple support functions is much simpler and general than the original one by Shafer.

  8. Nanoimprinted polymer solar cell.

    Science.gov (United States)

    Yang, Yi; Mielczarek, Kamil; Aryal, Mukti; Zakhidov, Anvar; Hu, Walter

    2012-04-24

    Among the various organic photovoltaic devices, the conjugated polymer/fullerene approach has drawn the most research interest. The performance of these types of solar cells is greatly determined by the nanoscale morphology of the two components (donor/acceptor) and the molecular orientation/crystallinity in the photoactive layer. A vertically bicontinuous and interdigitized heterojunction between donor and acceptor has been regarded as one of the ideal structures to enable both efficient charge separation and transport. Synergistic control of polymer orientation in the nanostructured heterojunction is also critical to improve the performance of polymer solar cells. Nanoimprint lithography has emerged as a new approach to simultaneously control both the heterojunction morphology and polymer chains in organic photovoltaics. Currently, in the area of nanoimprinted polymer solar cells, much progress has been achieved in the fabrication of nanostructured morphology, control of molecular orientation/crystallinity, deposition of acceptor materials, patterned electrodes, understanding of structure-property correlations, and device performance. This review article summarizes the recent studies on nanoimprinted polymer solar cells and discusses the outstanding challenges and opportunities for future work.

  9. Lattice of ℤ-module

    Directory of Open Access Journals (Sweden)

    Futa Yuichi

    2016-03-01

    Full Text Available In this article, we formalize the definition of lattice of ℤ-module and its properties in the Mizar system [5].We formally prove that scalar products in lattices are bilinear forms over the field of real numbers ℝ. We also formalize the definitions of positive definite and integral lattices and their properties. Lattice of ℤ-module is necessary for lattice problems, LLL (Lenstra, Lenstra and Lovász base reduction algorithm [14], and cryptographic systems with lattices [15] and coding theory [9].

  10. Lattice QCD on Non-Orientable Manifolds

    CERN Document Server

    Mages, Simon; Borsanyi, Szabolcs; Fodor, Zoltan; Katz, Sandor; Szabo, Kalman K

    2015-01-01

    A common problem in lattice QCD simulations on the torus is the extremely long autocorrelation time of the topological charge, when one approaches the continuum limit. The reason is the suppressed tunneling between topological sectors. The problem can be circumvented by replacing the torus with a different manifold, so that the field configuration space becomes connected. This can be achieved by using open boundary conditions on the fields, as proposed earlier. It has the side effect of breaking translational invariance completely. Here we propose to use a non-orientable manifold, and show how to define and simulate lattice QCD on it. We demonstrate in quenched simulations that this leads to a drastic reduction of the autocorrelation time. A feature of the new proposal is, that translational invariance is preserved up to exponentially small corrections. A Dirac-fermion on a non-orientable manifold poses a challenge to numerical simulations: the fermion determinant becomes complex. We propose two approaches to...

  11. An Algorithm on Generating Lattice Based on Layered Concept Lattice

    Directory of Open Access Journals (Sweden)

    Zhang Chang-sheng

    2013-08-01

    Full Text Available Concept lattice is an effective tool for data analysis and rule extraction, a bottleneck factor on impacting the applications of concept lattice is how to generate lattice efficiently. In this paper, an algorithm LCLG on generating lattice in batch processing based on layered concept lattice is developed, this algorithm is based on layered concept lattice, the lattice is generated downward layer by layer through concept nodes and provisional nodes in current layer; the concept nodes are found parent-child relationships upward layer by layer, then the Hasse diagram of inter-layer connection is generated; in the generated process of the lattice nodes in each layer, we do the pruning operations dynamically according to relevant properties, and delete some unnecessary nodes, such that the generating speed is improved greatly; the experimental results demonstrate that the proposed algorithm has good performance.

  12. Wilson loops with arbitrary charges

    CERN Document Server

    Korcyl, Piotr; Wosiek, Jacek

    2014-01-01

    We discuss how to implement, in lattice gauge theories, external charges which are not commensurate with an elementary gauge coupling. It is shown that an arbitrary, real power of a standard Wilson loop (or Polyakov line) can be defined and consistently computed in lattice formulation of non-abelian, two dimensional gauge theories. However, such an observable can excite quantum states with integer fluxes only. Since the non-integer fluxes are not in the spectrum of the theory they cannot be created, no matter which observable is chosen. Also the continuum limit of above averages does not exist unless the powers in question are in fact integer. On the other hand, a new continuum limit exists, which is rather intuitive, and where above observables make perfect sense and lead to the string tension proportional to the square of arbitrary (non necessary commensurate with gauge coupling) charge.

  13. Fermionic quantum critical point of spinless fermions on a honeycomb lattice

    NARCIS (Netherlands)

    Wang, L.; Corboz, P.; Troyer, M.

    2014-01-01

    Spinless fermions on a honeycomb lattice provide a minimal realization of lattice Dirac fermions. Repulsive interactions between nearest neighbors drive a quantum phase transition from a Dirac semimetal to a charge-density-wave state through a fermionic quantum critical point, where the coupling of

  14. The JKJ Lattice

    Science.gov (United States)

    Shigaki, Kenta; Noda, Fumiaki; Yamamoto, Kazami; Machida, Shinji; Molodojentsev, Alexander; Ishi, Yoshihiro

    2002-12-01

    The JKJ high-intensity proton accelerator facility consists of a 400-MeV linac, a 3-GeV 1-MW rapid-cycling synchrotron and a 50-GeV 0.75-MW synchrotron. The lattice and beam dynamics design of the two synchrotrons are reported.

  15. Quantum lattice problems

    NARCIS (Netherlands)

    de Raedt, Hans; von der Linden, W.; Binder, K

    1995-01-01

    In this chapter we review methods currently used to perform Monte Carlo calculations for quantum lattice models. A detailed exposition is given of the formalism underlying the construction of the simulation algorithms. We discuss the fundamental and technical difficulties that are encountered and gi

  16. Measuring on Lattices

    CERN Document Server

    Knuth, Kevin H

    2009-01-01

    Previous derivations of the sum and product rules of probability theory relied on the algebraic properties of Boolean logic. Here they are derived within a more general framework based on lattice theory. The result is a new foundation of probability theory that encompasses and generalizes both the Cox and Kolmogorov formulations. In this picture probability is a bi-valuation defined on a lattice of statements that quantifies the degree to which one statement implies another. The sum rule is a constraint equation that ensures that valuations are assigned so as to not violate associativity of the lattice join and meet. The product rule is much more interesting in that there are actually two product rules: one is a constraint equation arises from associativity of the direct products of lattices, and the other a constraint equation derived from associativity of changes of context. The generality of this formalism enables one to derive the traditionally assumed condition of additivity in measure theory, as well in...

  17. Lattice Multiverse Models

    OpenAIRE

    Williamson, S. Gill

    2010-01-01

    Will the cosmological multiverse, when described mathematically, have easily stated properties that are impossible to prove or disprove using mathematical physics? We explore this question by constructing lattice multiverses which exhibit such behavior even though they are much simpler mathematically than any likely cosmological multiverse.

  18. Phenomenology from lattice QCD

    CERN Document Server

    Lellouch, L P

    2003-01-01

    After a short presentation of lattice QCD and some of its current practical limitations, I review recent progress in applications to phenomenology. Emphasis is placed on heavy-quark masses and on hadronic weak matrix elements relevant for constraining the CKM unitarity triangle. The main numerical results are highlighted in boxes.

  19. Noetherian and Artinian Lattices

    Directory of Open Access Journals (Sweden)

    Derya Keskin Tütüncü

    2012-01-01

    Full Text Available It is proved that if L is a complete modular lattice which is compactly generated, then Rad(L/0 is Artinian if, and only if for every small element a of L, the sublattice a/0 is Artinian if, and only if L satisfies DCC on small elements.

  20. Quark–gluon plasma phenomenology from anisotropic lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Skullerud, Jon-Ivar; Kelly, Aoife [Department of Mathematical Physics, Maynooth University, Maynooth, Co Kildare (Ireland); Aarts, Gert; Allton, Chris; Amato, Alessandro; Evans, P. Wynne M.; Hands, Simon [Department of Physics, Swansea University, Swansea SA2 8PP, Wales (United Kingdom); Burnier, Yannis [Institut de Théorie des Phénomènes Physiques, Ecole Polytechnique Fédérale de Lausanne, CH–1015 Lausanne (Switzerland); Giudice, Pietro [Institut für Theoretische Physik, Universität Münster, D–48149 Münster (Germany); Harris, Tim; Ryan, Sinéad M. [School of Mathematics, Trinity College, Dublin 2 (Ireland); Kim, Seyong [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Lombardo, Maria Paola [INFN–Laboratori Nazionali di Frascati, I–00044 Frascati (RM) (Italy); Oktay, Mehmet B. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States); Rothkopf, Alexander [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, D–69120 Heidelberg (Germany)

    2016-01-22

    The FASTSUM collaboration has been carrying out simulations of N{sub f} = 2 + 1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics.

  1. Kostka polynomials and energy functions in solvable lattice models

    CERN Document Server

    Nakayashiki, A; Nakayashiki, Atsushi; Yamada, Yasuhiko

    1995-01-01

    The relation between the charge of Lascoux-Schuzenberger and the energy function in solvable lattice models is clarified. As an application, A.N.Kirillov's conjecture on the expression of the branching coefficient of {\\widehat {sl_n}}/{sl_n} as a limit of Kostka polynomials is proved.

  2. Conjugated Polymer Solar Cells

    Science.gov (United States)

    2006-05-01

    oxygen since their EPR and conductivity data indicated the presence of unpaired charges. On the other hand, intramolecular CT complexes have recently...been reported for polythiophene [2], where weak CT occurs from a polymer unit cell to the covalently bonded acceptor molecule. Nevertheless, it was...intracavity optical doubler (532 nm), diode lasers (670, 810 nm) and light emitting diodes (490, 630 nm). Measurements were conducted for pump intensity 0.1

  3. Thermoelectric Properties of Conducting Polymers

    Science.gov (United States)

    1994-07-01

    conductivity of highly ordered pyrolytic graphite and benzene-derived graphite fiber. For a heat treament temperature (HTT) of 2900 °C, the unstretched film has... heat transmission is 5 important. The electrons responsible for electrical conductivity in metals also allow heat transmission by electrons, K. in Fig. 1... Heat transmission in polymers is by means of lattice vibrations, K, which do not contribute to electrical conductvity. Previous work with conducting

  4. Elastic Behavior of Polymer Chains

    Institute of Scientific and Technical Information of China (English)

    Teng Lu; Tao Chen; Hao-jun Liang

    2008-01-01

    The elastic behavior of the polymer chain was investigated in a three-dimensional off-lattice model. We sample more than 109 conformations of each kind of polymer chain by using a Monte Carlo algorithm, then analyze them with the non-Gaussian theory of rubberlike elasticity, and end with a statistical study. Through observing the effect of the chain flexibility and the stretching ratio on the mean-square end-to-end distance,the average energy, the average Helmholtz free energy, the elastic force, the contribution of energy to the elastic force, and the entropy contribution to elastic force of the polymer chain, we find that a rigid polymer chain is much easier to stretch than a flexible polymer chain. Also, a rigid polymer chain will become difficult to stretch only at a quite high stretching ratio because of the effect of the entropy contribution.These results of our simulation calculation may explain some of the macroscopic phenomena of polymer and biomacromolecular elasticity.

  5. Basis reduction for layered lattices

    NARCIS (Netherlands)

    Torreão Dassen, Erwin

    2011-01-01

    We develop the theory of layered Euclidean spaces and layered lattices. We present algorithms to compute both Gram-Schmidt and reduced bases in this generalized setting. A layered lattice can be seen as lattices where certain directions have infinite weight. It can also be interpre

  6. Spin qubits in antidot lattices

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Flindt, Christian; Mortensen, Niels Asger;

    2008-01-01

    and density of states for a periodic potential modulation, referred to as an antidot lattice, and find that localized states appear, when designed defects are introduced in the lattice. Such defect states may form the building blocks for quantum computing in a large antidot lattice, allowing for coherent...

  7. Polymer Brushes

    NARCIS (Netherlands)

    Vos, de W.M.; Kleijn, J.M.; Keizer, de A.; Cosgrove, T.; Cohen Stuart, M.A.

    2010-01-01

    A polymer brush can be defined as a dense array of polymers end-attached to an interface that stretch out into the surrounding medium. Polymer brushes have been investigated for the past 30 years and have shown to be an extremely useful tool to control interfacial properties. This review is intended

  8. Algorithms for Disconnected Diagrams in Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Gambhir, Arjun Singh [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Stathopoulos, Andreas [College of William and Mary, Williamsburg, VA (United States); Orginos, Konstantinos [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Yoon, Boram [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gupta, Rajan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Syritsyn, Sergey [Stony Brook Univ., NY (United States)

    2016-11-01

    Computing disconnected diagrams in Lattice QCD (operator insertion in a quark loop) entails the computationally demanding problem of taking the trace of the all to all quark propagator. We first outline the basic algorithm used to compute a quark loop as well as improvements to this method. Then, we motivate and introduce an algorithm based on the synergy between hierarchical probing and singular value deflation. We present results for the chiral condensate using a 2+1-flavor clover ensemble and compare estimates of the nucleon charges with the basic algorithm.

  9. Lattice Chiral Fermions Through Gauge Fixing

    CERN Document Server

    Bock, W; Shamir, Y; Bock, Wolfgang; Golterman, Maarten; Shamir, Yigal

    1998-01-01

    We study a concrete lattice regularization of a U(1) chiral gauge theory. We use Wilson fermions, and include a Lorentz gauge-fixing term and a gauge-boson mass counterterm. For a reduced version of the model, in which the gauge fields are constrained to the trivial orbit, we show that there are no species doublers, and that the fermion spectrum contains only the desired states in the continuum limit, namely charged left-handed (LH) fermions and neutral right-handed (RH) fermions.

  10. Missing strange resonances in Lattice QCD

    CERN Document Server

    Marczenko, Michał

    2016-01-01

    Recent Lattice QCD (LQCD) studies suggest that there are missing resonances in the strange sector of the Hadron Resonance Gas (HRG) model. By adopting the continuous Hagedorn mass spectrum, we present how different medium compositions influence the HRG predictions of conserved charge fluctuations. It is shown that missing strange resonances may be partially accounted for by applying the Hagedorn mass spectrum extracted from experimentally established hadrons. On the other hand, the strange-baryonic spectra, extracted from LQCD results for fluctuations, are found to be consistent with the unconfirmed states in the Particle Data Group (PDG) database, whilst the strange-mesonic spectrum points towards yet undiscovered states in the intermediate mass region.

  11. Algorithms for Disconnected Diagrams in Lattice QCD

    CERN Document Server

    Gambhir, Arjun Singh; Orginos, Kostas; Yoon, Boram; Gupta, Rajan; Syritsyn, Sergey

    2016-01-01

    Computing disconnected diagrams in Lattice QCD (operator insertion in a quark loop) entails the computationally demanding problem of taking the trace of the all to all quark propagator. We first outline the basic algorithm used to compute a quark loop as well as improvements to this method. Then, we motivate and introduce an algorithm based on the synergy between hierarchical probing and singular value deflation. We present results for the chiral condensate using a 2+1-flavor clover ensemble and compare estimates of the nucleon charges with the basic algorithm.

  12. Kondo lattice without Nozieres exhaustion effect.

    Energy Technology Data Exchange (ETDEWEB)

    Kikoin, K.; Kiselev, M. N.; Materials Science Division; Ben-Gurion Univ. of the Negev; Ludwig-Maximilians Univ.

    2006-01-01

    We discuss the properties of layered Anderson/Kondo lattices with metallic electrons confined in 2D xy planes and local spins in insulating layers forming chains in the z direction. Each spin in this model possesses its own 2D Kondo cloud, so that the Nozieres exhaustion problem does not occur. The high-temperature perturbational description is matched to exact low-T Bethe-ansatz solution. The excitation spectrum of the model is gapless both in charge and spin sectors. The disordered phases and possible experimental realizations of the model are briefly discussed.

  13. Preparation and characterization of organic polymer modified composite polyaluminum chloride

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Compared with traditional aluminum salts, polyaluminum chloride (PACl) has better coagulation-flocculation performance in turbidity removal. However, it is still inferior to organic polymers in terms of bridging function. In order to improve the aggregating property of PACl, different composite PACl flocculants were prepared with various organic polymers. The effect of organic polymer on the distribution of Al (Ⅲ) species in composite flocculants was studied using 27Al NMR and Al-ferron complexation methods. The charge neutralization and surface adsorption characteristics of composite flocculants were also investigated. Jar tests were conducted to evaluate the turbidity removal efficacy of organic polymer modified composite flocculants. The study shows that cationic polymer and anionic polymer have significant influences on the coagulation-flocculation behaviors of PACl. Both cationic and anionic polymers can improve the turbidity removal performance of PACl but the mechanisms are much different: cationic organic polymer mainly increases the charge neutralization ability, but anionic polymer mainly enhances the bridging function.

  14. Introduction to lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, R.

    1998-12-31

    The goal of the lectures on lattice QCD (LQCD) is to provide an overview of both the technical issues and the progress made so far in obtaining phenomenologically useful numbers. The lectures consist of three parts. The author`s charter is to provide an introduction to LQCD and outline the scope of LQCD calculations. In the second set of lectures, Guido Martinelli will discuss the progress they have made so far in obtaining results, and their impact on Standard Model phenomenology. Finally, Martin Luescher will discuss the topical subjects of chiral symmetry, improved formulation of lattice QCD, and the impact these improvements will have on the quality of results expected from the next generation of simulations.

  15. Lattice Quantum Chromodynamics

    Science.gov (United States)

    Sachrajda, C. T.

    2016-10-01

    I review the the application of the lattice formulation of QCD and large-scale numerical simulations to the evaluation of non-perturbative hadronic effects in Standard Model Phenomenology. I present an introduction to the elements of the calculations and discuss the limitations both in the range of quantities which can be studied and in the precision of the results. I focus particularly on the extraction of the QCD parameters, i.e. the quark masses and the strong coupling constant, and on important quantities in flavour physics. Lattice QCD is playing a central role in quantifying the hadronic effects necessary for the development of precision flavour physics and its use in exploring the limits of the Standard Model and in searches for inconsistencies which would signal the presence of new physics.

  16. Lattices of dielectric resonators

    CERN Document Server

    Trubin, Alexander

    2016-01-01

    This book provides the analytical theory of complex systems composed of a large number of high-Q dielectric resonators. Spherical and cylindrical dielectric resonators with inferior and also whispering gallery oscillations allocated in various lattices are considered. A new approach to S-matrix parameter calculations based on perturbation theory of Maxwell equations, developed for a number of high-Q dielectric bodies, is introduced. All physical relationships are obtained in analytical form and are suitable for further computations. Essential attention is given to a new unified formalism of the description of scattering processes. The general scattering task for coupled eigen oscillations of the whole system of dielectric resonators is described. The equations for the  expansion coefficients are explained in an applicable way. The temporal Green functions for the dielectric resonator are presented. The scattering process of short pulses in dielectric filter structures, dielectric antennas  and lattices of d...

  17. Lattice QCD for Cosmology

    CERN Document Server

    Borsanyi, Sz; Kampert, K H; Katz, S D; Kawanai, T; Kovacs, T G; Mages, S W; Pasztor, A; Pittler, F; Redondo, J; Ringwald, A; Szabo, K K

    2016-01-01

    We present a full result for the equation of state (EoS) in 2+1+1 (up/down, strange and charm quarks are present) flavour lattice QCD. We extend this analysis and give the equation of state in 2+1+1+1 flavour QCD. In order to describe the evolution of the universe from temperatures several hundreds of GeV to several tens of MeV we also include the known effects of the electroweak theory and give the effective degree of freedoms. As another application of lattice QCD we calculate the topological susceptibility (chi) up to the few GeV temperature region. These two results, EoS and chi, can be used to predict the dark matter axion's mass in the post-inflation scenario and/or give the relationship between the axion's mass and the universal axionic angle, which acts as a initial condition of our universe.

  18. Solitons in nonlinear lattices

    CERN Document Server

    Kartashov, Yaroslav V; Torner, Lluis

    2010-01-01

    This article offers a comprehensive survey of results obtained for solitons and complex nonlinear wave patterns supported by purely nonlinear lattices (NLs), which represent a spatially periodic modulation of the local strength and sign of the nonlinearity, and their combinations with linear lattices. A majority of the results obtained, thus far, in this field and reviewed in this article are theoretical. Nevertheless, relevant experimental settings are surveyed too, with emphasis on perspectives for implementation of the theoretical predictions in the experiment. Physical systems discussed in the review belong to the realms of nonlinear optics (including artificial optical media, such as photonic crystals, and plasmonics) and Bose-Einstein condensation (BEC). The solitons are considered in one, two, and three dimensions (1D, 2D, and 3D). Basic properties of the solitons presented in the review are their existence, stability, and mobility. Although the field is still far from completion, general conclusions c...

  19. Parametric lattice Boltzmann method

    Science.gov (United States)

    Shim, Jae Wan

    2017-06-01

    The discretized equilibrium distributions of the lattice Boltzmann method are presented by using the coefficients of the Lagrange interpolating polynomials that pass through the points related to discrete velocities and using moments of the Maxwell-Boltzmann distribution. The ranges of flow velocity and temperature providing positive valued distributions vary with regulating discrete velocities as parameters. New isothermal and thermal compressible models are proposed for flows of the level of the isothermal and thermal compressible Navier-Stokes equations. Thermal compressible shock tube flows are simulated by only five on-lattice discrete velocities. Two-dimensional isothermal and thermal vortices provoked by the Kelvin-Helmholtz instability are simulated by the parametric models.

  20. Varieties of lattices

    CERN Document Server

    Jipsen, Peter

    1992-01-01

    The study of lattice varieties is a field that has experienced rapid growth in the last 30 years, but many of the interesting and deep results discovered in that period have so far only appeared in research papers. The aim of this monograph is to present the main results about modular and nonmodular varieties, equational bases and the amalgamation property in a uniform way. The first chapter covers preliminaries that make the material accessible to anyone who has had an introductory course in universal algebra. Each subsequent chapter begins with a short historical introduction which sites the original references and then presents the results with complete proofs (in nearly all cases). Numerous diagrams illustrate the beauty of lattice theory and aid in the visualization of many proofs. An extensive index and bibliography also make the monograph a useful reference work.